Simplified the Constraint removal logic

Simplified the Constraint removal logic

[problem]      Memory corruption caused by unsafe calls to SetWeight
[cause]        The root cause is the Constraint using the ProxyObject::Observer interface
               for two different purposes; firstly to find out about parent on/off stage
               behavior, and also to track the objects providing property inputs.
[solution]     Reduced the complexity of the constraint logic; removed observer usage
               for the parent object, moved code from templates to common base class.
               Deprecated the (unused) SetRemoveTime API bloat.

Change-Id: I4d789143f4dc36767cbc91adf63d47f488c37e1b