1) refactored for support of different server types besides postgres
2) DataTableFactory for encapsulating of table data implementations
3) introduction of ExecutionGraph in preparation of sending data in chunks
4) reorganized header files for better extension development
5) treat external files (xlsx/csv) as processable queries (ResourceQueryExecution)

Squashed commit of the following:

commit 927c13e8f520cbeb2d22918dad9db6bd42847932
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Thu Jun 12 15:38:16 2014 +0200

    prepare upload to github

commit 60d88d35242af2636e87d35e5fad5153c34720dd
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Thu Jun 12 10:24:41 2014 +0200

    make table data constructors available from TableDataFactory only

commit 2ee9e8c27df27cbae03d11343f71c5f90ffd49da
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Wed Jun 11 18:30:58 2014 +0200

    isolate table data constructors

commit 4570749d0b727b1691a475a184bc61cf3d2565ac
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Wed Jun 11 17:18:48 2014 +0200

    lookup QueryExecution via ExtensionLoader

commit 0efc56fa730cf74f9915420a31b6b4472ebfa726
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Wed Jun 11 15:36:16 2014 +0200

    load external files via ResourceQueryExecption

commit b4943f510b3d2267344967e80ae7950a5712c1b4
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Wed Jun 11 11:35:15 2014 +0200

    generic url: removed postgres specific Connection class

commit d06bdebe04074c9f0007e4eab02a7ea69cde6816
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Wed Jun 11 09:26:05 2014 +0200

    prepare to replace postgres specific Connection class to Url class

commit 3f3262753a4c09246d759ff5926b91bdbedd6190
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Tue Jun 10 15:48:18 2014 +0200

    prepare Query class to handle different query types

commit 9b00126c861a613a1d199e8a94e0fd0972ee06fc
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Tue Jun 10 14:30:41 2014 +0200

    moved AsyncQueryExecutor to PGQueryExecution. QueryProcessor almost generic

commit 5b6ba7e659b950c2fcea4cf9db78066ab8f16351
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Tue Jun 10 12:45:25 2014 +0200

    extracted pg specific code to PGQueryExecution

commit c4c96f5b162e3b0415aa8dc01208426731d9d899
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Tue Jun 10 11:26:59 2014 +0200

    transition done when all out channels closed

commit 43fbfa689b885288ae93ae8b9169a1c64106d303
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Mon Jun 9 18:46:59 2014 +0200

    remove redundant code

commit e12ee21cbfd0d835cc7d61a408285028b05dfbe2
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Mon Jun 9 18:29:11 2014 +0200

    remove redundant code

commit 74d3082c6bff6a282658b3a4e0c38c8b38aabe4b
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Sat Jun 7 14:25:20 2014 +0200

    removed transitions from query execution

commit f2cb09b1096bac142800cf6e1eef309a33d4d479
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Sat Jun 7 13:51:55 2014 +0200

    removed targets from transition

commit fbe56e95ea99ec96d4f4737e1edb51db5560862d
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Sat Jun 7 13:08:27 2014 +0200

    removed source executions from transitions

commit 4895024dffe32efb1069e9af238fe592cc0a40b0
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Sat Jun 7 12:18:07 2014 +0200

    prepared decoupling of transition and execution

commit 973bceb94e4b948134f01368cf3bd734477c7718
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Sat Jun 7 11:02:48 2014 +0200

    dump execution plan channel based / create channels when populating transitions

commit 252e73e427aa3fc91bed691ab2031af5f7d02b6f
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Mon Jun 2 10:03:36 2014 +0200

    move dumpExecutionPlan to ExecutionGraph

commit 9f1417af8195603478beed92dd730ac3f2664209
Author: Arnd Brusdeilins <arnd.brusdeilins@zalando.de>
Date:   Mon Jun 2 09:42:05 2014 +0200

    moved graph element to new ExecutionGraph class