Added check for readonly properties when evaluating incoming jsonpatches. Fixes #1687.
Added unittest that tests incoming jsonpatches.
Moved unittests for jsonpatch from project Starcounter.Apps.Test to Starcounter.XSON.Tests (where all the other tests for jsonpatch is) and refactored some of the tests.
Moved the check for readonly template to just before it is called instead of when evaluating the jsonpointer.
Merge branch 'issue/1687' into develop