Merge pull request #11 from bantolov/master

Build 0.9.7
CreationTime refactoring
Implementation moved from database to object model (data import should not change the migrated creation time)
Merge pull request #13 from kmeze/master

CreationTime refactoring
New concept SystemRequired.
Bugfix:
Constraint name was not unique.
Removed backing fields for properties in object model.
Also removed default values of ShortString (empty string) and ID (NewGuid) fields.
Every use of backing fields was a potential bug: NHibernate proxies ignored default setter and getter methods so default property values sometimes caused mismatch between a property and the corresponding field.
Bugfix: Recursive updates with KeepSynchronized could cause infinite loop even if there is nothing to update.
New concept: DenyUserEdit, for a property that may only be changed by the server, not by a client Save request.
It should be used rarely, since mixing editable and non-editable properties in the same entity is not the best design.
DenyUserEdit is based on checkUserPermissions parameter of repositories' Save function, that is intended to be used for advanced permissions (row, column permissions and other).
Merge branch 'master' of https://github.com/kmeze/Rhetos

Conflicts:
	CommonConcepts/CommonConceptsTest/CommonConcepts.Test/CommonConcepts.Test.csproj
	CommonConcepts/CommonConceptsTest/DslScripts/SimpleBusinessLogicTest.rhe