Refactored Solver interface to seperate meta data handling from content

Now, the content changes are provided to the solver, which should react on
the given informations and should not down/upload content if the content is
not marked as changed. This behaviour must be implemented in the next steps.
Updated DotCMIS submodule to use the latest version
Improved unit tests
Ensured that the LastModificationDate of a file stays untouched on setting extended attributes
Added solver template for local and remote change situation
Reverted the update of the submodule to get back to a stable version
Changed to fixed and latest version of DotCMIS
Fixed IOException on root folder initialization
Added CreationTime to IFileSystemInfo as readonly property
The local added and changed solver do not modify the LastModificationDate

Ensured that the last modification date of an uploaded file/folder are
untouched on uploading.
Added property to request if the server is able to set the last modification of a cmis object

Normally, this feature is not available on CMIS Server, but it will be on GDS
Ensured that local modification date is not touched on uploads
Moved CmisConvenienceExtenders to CmisSync.Lib
Added possibility to get ContentStreamHash from a IDocument instance
Tried to fix progress stream reporting length while uploading
reverted changes on Progress stream to avoid exception on windows
whitespaces
Added detection of equal remote content on content change events
Fixed some bugs in descendants crawler and added better verification in tests
Improved the ContentStreamHash handling and testing