Add @Accessor annoation to manipulate the EntityAccessor.
Support $id==null in EntityDataProvider::isUniqueValue()
Read and write raw properties when cloning an EntityModel.
Fix regular expression of getter method detection.
Fix missing properties in EntityAccessor::setRawProperties()
Allow clearing the primary key in EntityAccessor::setPrimaryKey().
When generating a new alias, suffix with an index on duplicates.
Merge branch 'release/2.1'
Merge tag '2.1' into develop

Version 2.1