Added DayDate and start with gregorian calendar

Squashed commit of the following:

commit be6b8bc6d86b6e3c6a2e12a8a9d1f95c840d51fa
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Oct 27 11:31:05 2013 +0100

    better class names

commit fa86118a2ec3fdbced888ab2188297c502415e2d
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Oct 27 11:27:50 2013 +0100

    clean up

    adjusted types and class names

commit 075c2e41a5a603a17f711816b74b6a573d9d423a
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Oct 27 11:16:10 2013 +0100

    looks good now

commit 7c3f236b2422e0e120e3367266a9002ae68d82d5
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Fri Oct 4 12:25:37 2013 +0200

    cleaned a bit the code

commit f4de68c4ac9f28a0982749e1f7a7e2af4b373ab5
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Wed Jun 12 21:05:07 2013 +0200

    on greg to day cal

commit 2b1d1a93a7065db5dda5bba162d2e060f974b4ae
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Tue Jun 11 20:15:25 2013 +0200

    implementing gregdate

commit 278229f226309da3f3ad73779811f2fc0c4c0c7b
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Tue Jun 11 19:48:44 2013 +0200

    wrote tests

commit 7e8da10d9a7521848c27721693302f9381598095
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Tue Jun 11 19:48:21 2013 +0200

    wrote tests

commit 882310fe38ed4b306d17686211314db8407fc2ff
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Tue Jun 11 18:59:19 2013 +0200

    wrote tests

commit 3125a040f63eff2843f1d1da61c4c593d10bb164
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Mon Jun 10 23:13:08 2013 +0200

    second addition looks good, now we need some tests

commit 7b0665ca50e6ad9457896647bcc76e5e59bff469
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Mon Jun 10 23:06:07 2013 +0200

    looks good

commit bd59bfb38b2b8648679ddde77820839a444ae9a0
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Mon Jun 10 23:01:01 2013 +0200

    ok how to solve this

commit 2f02ee64cd6c621d12584d5a5f985eead1a1d7f9
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Mon Jun 10 22:47:22 2013 +0200

    a bit more abstract

commit 3ebafd8b6fbaf4e9ddcc2b0931919c87bf823fce
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 22:46:54 2013 +0200

    ok tests fail again

commit c20082fc95b929e13dc7c5cdf44c7a6a708b3a97
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 22:44:56 2013 +0200

    moar tests

commit 87c781165e062dccf751ec2d9f205559ce7de486
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 22:44:14 2013 +0200

    moar tests

commit 51637003e27d00ab308a43569bed4ed498b84b5b
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 22:23:12 2013 +0200

    corrected day operations

commit edb69c2dfa09e318c28360530af763baa4b3518f
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 22:13:13 2013 +0200

    corrected day operations

commit 43b5e60bce88a357b6cb306e29b8b4aa627e1d13
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 22:02:49 2013 +0200

    tests look good

commit 6133c2b879cc7fb3d21c66fab3e71f3df3f7fc33
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 21:04:42 2013 +0200

    now tests

commit af0d9642c317ac1196116b3bd2249224fde1d77e
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 20:58:44 2013 +0200

    test for add and delete

commit 1e70e4d613f3afc7c7c201dfbb99e4ef328622d9
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 18:59:56 2013 +0200

    correction

commit f67c22ee62a36a5db9f016b37319dd4ab9d82071
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 18:58:52 2013 +0200

    wrote operators

commit e59767c607ed89e0a8879006807dca3483424775
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 17:57:11 2013 +0200

    add tests

commit af789544677f3be3ecea37497b5ce8af344599ad
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 15:50:02 2013 +0200

    working on operations

commit ef0f4ef05f337059272f28295cfcb6c18c909edd
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 15:49:31 2013 +0200

    working on operations

commit 31205607068076960125eb5d79fc35404fd67512
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 15:35:05 2013 +0200

    working on operations

commit 4e20a0a3538db59ac8b563cec488cb19bd1e2356
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 15:30:04 2013 +0200

    working on operations

commit 9deef69a97a681b6cb76758552e9c01fa2e19a8f
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 15:22:12 2013 +0200

    added randomized tests for the dates

commit c17a656609ffd75ae923a05ffd6d9cf5e95fb99a
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 15:15:07 2013 +0200

    fixed error

commit af51a57c544a1f5c16a5c99fef2406a3d9684ee9
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 15:10:55 2013 +0200

    optimized tests

commit b066e445f5412b0c6ee0fe51f99c52df8a504d2b
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 15:06:08 2013 +0200

    writing tests

commit 26d0eb80706f1a288f5d32c2d866037897a1376d
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 14:58:07 2013 +0200

    looks good

commit f250015eebd310677d458c3d3aab389473988891
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 14:44:18 2013 +0200

    typo (intellij makes it possible)

commit b4ea580e3c0dd59fb6489ba550109caa1ba1f374
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 14:43:46 2013 +0200

    working on the day date

commit 847a7e860581dc6dd083a4c7a9c9b1b21bd9e5ce
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 14:01:33 2013 +0200

    working on a good system of calendars

commit 19aba98c8839a1fbb13023097e96d62d295d9ffe
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 13:31:48 2013 +0200

    refdate should be in core not in base

commit a0f6baafd77b9a95a181e6ab2d0f793c59036c26
Author: Ingolf Wagner <palipalo9@googlemail.com>
Date:   Sun Jun 9 13:27:48 2013 +0200

    refdate package clean up