Lots of EXIF mode fixes and improvements by Dennis Real (closes #87)

Squashed commit of the following:

commit 58dd2e303c5ee380527d92a3fa3d6baeeacb50a1
Merge: cf6f032 82a976e
Author: Dennis Real <github@tildepipe.org>
Date:   Sat Mar 31 18:43:47 2012 +0200

    Merge branch 'master' of git://github.com/derf/feh

commit cf6f0320c15abd753951990a963d5c94b180bbde
Merge: 10b7b1e 877e634
Author: Dennis Real <github@tildepipe.org>
Date:   Sun Mar 25 19:07:30 2012 +0200

    Merge branch 'master' of git://github.com/derf/feh

commit 10b7b1e3e10ba650b240a742947cb6850bbadd23
Author: Dennis Real <github@tildepipe.org>
Date:   Sat Mar 24 14:41:15 2012 +0100

    Support for Canon Exif makernote tags

commit 3c284dc81dcb26249114b7ecf32ed0000f492b8b
Author: Dennis Real <github@tildepipe.org>
Date:   Thu Mar 22 19:44:32 2012 +0100

    Support for Active D-Lightning

commit ad5aea8cb853cc9d1b322c69f4812ad0bcb08ef3
Merge: cc6de20 9c43b64
Author: Dennis Real <github@tildepipe.org>
Date:   Thu Mar 22 19:01:38 2012 +0100

    Merge remote branch 'upstream/master'

commit cc6de20061eaa7172aa0184e03df947da14d713e
Author: Dennis Real <github@tildepipe.org>
Date:   Thu Mar 22 19:00:30 2012 +0100

    Nikon makernote parts changed

commit e401bd9c78a82b8290ec524e56b7c832631725e6
Author: Dennis Real <github@tildepipe.org>
Date:   Wed Mar 21 19:47:15 2012 +0100

    1. Own module for nikon maker notes
    2. Support for AFInfo2

commit 39cbd1ed2b6693beea5e974a6ae83207c6e9a826
Merge: 9e1bbf8 a100123
Author: Dennis Real <github@tildepipe.org>
Date:   Fri Mar 16 22:22:28 2012 +0100

    Merge remote branch 'upstream/master'

commit 9e1bbf874500e99506baffec3c6b54ed04e60a2f
Author: Dennis Real <github@tildepipe.org>
Date:   Fri Mar 16 22:20:58 2012 +0100

    - exif handling changed
    - gps info added if available

commit 8e96382805eb77a82209df9d71dbf9c0dd1c4cdb
Merge: 77fa5ac 29cd868
Author: Dennis Real <github@tildepipe.org>
Date:   Fri Mar 16 19:13:47 2012 +0100

    Merge branch 'master' of git://github.com/derf/feh

commit 77fa5aca182435f2771511832ea198d027393ceb
Merge: 93a90e6 3b2756b
Author: Dennis Real <github@tildepipe.org>
Date:   Wed Mar 7 17:18:07 2012 +0100

    Merge branch 'master' of git://github.com/derf/feh

commit 93a90e60d0cf093ca71c34f4f5dbfde974f433f0
Merge: a81465d 52d5da9
Author: Dennis Real <github@tildepipe.org>
Date:   Tue Mar 6 21:42:40 2012 +0100

    Merge branch 'master' of git://github.com/derf/feh

commit a81465d019593cfd1e506eb66f20f6b5e10488f3
Merge: a19e50d 31afac4
Author: Dennis Real <github@tildepipe.org>
Date:   Mon Mar 5 17:23:40 2012 +0100

    Merge branch 'master' of git://github.com/derf/feh

commit a19e50deb749c5188bdbc75a5c1cd6ab1f3f3a3a
Merge: 1c89da1 fe9a16b
Author: Dennis Real <github@tildepipe.org>
Date:   Sun Mar 4 15:35:45 2012 +0100

    Merge branch 'master' of ssh://github.com/reald/feh

commit 1c89da1269089d98529a6635c36d014da1b08eb4
Author: Dennis Real <github@tildepipe.org>
Date:   Tue Feb 28 22:37:22 2012 +0100

    test case adapted to new testfile

commit bb3c9d3571e43f913c6f659fefd9cd34971fd004
Author: Dennis Real <github@tildepipe.org>
Date:   Tue Feb 28 22:34:51 2012 +0100

    test file with some exif data added

commit fe9a16bce3f06d45acf103fc4439c1af2dc4ac6c
Author: Dennis Real <github@tildepipe.org>
Date:   Tue Feb 28 22:37:22 2012 +0100

    test case adapted to new testfile

commit e0bedc0438cf4ab4eafe43afca0886ad63591560
Merge: 46801fe 69ecc5c
Author: Dennis Real <github@tildepipe.org>
Date:   Tue Feb 28 22:36:08 2012 +0100

    Merge remote branch 'upstream/master'

commit 46801fee8de26f4e0af2ed294c3a4f7fc1c45ca3
Author: Dennis Real <github@tildepipe.org>
Date:   Tue Feb 28 22:34:51 2012 +0100

    test file with some exif data added
Merge branch 'master' of git://github.com/derf/feh