Refactoring of RowPermissionsRead and implementation of RowPermissionsWrite
* Renamed RowPermissions filter names to RowPermissionsReadItems, RowPermissionsWriteItems
* RowPermissions concept will add both RowPermissionsRead and RowPermissionsWrite concepts with the same expression
* CheckAllItemsWithinFilter is now public GenericRepository method for generic purpose
* RowPermissions are now checked in the respective command implementation layer (ReadCommand, SaveEntityCommand), NOT GenericRepository
* Various minor code refactoring related to RowPermissions and related methods/classes
* Updated CommonConceptsTest to cover all of the new features and changes in this commit
Code review changes
* RowPermissionsWrite will now check updating items before and after update, to prevent changing entity from not permitted to permitted state
* Added test for the above case
* Minor code corrections
Merge pull request #30 from sstublic/master

RowPermissionsWrite
Merge branch 'master' of https://github.com/Rhetos/Rhetos

Conflicts:
	CommonConcepts/Plugins/Rhetos.Dsl.DefaultConcepts/Rhetos.Dsl.DefaultConcepts.csproj
Fixing row permissions rules after merge.
Minor refactoring.
Refactoring server command utilities out of GenericRepository.