Separate RPCHandler to PropertyHandler and ActionHandler

[VigneshVSV]

Currently, we have only one HTTP handler for property read-write and action execution called RPCHandler.

To support different HTTP headers for properties and actions separately, it would be useful to separate them. Further, this gives flexibility to the user who can subclass the handlers separately for properties and actions instead of a common RPC operation handler.

Possible steps

• clearly define the headers for property execution and action execution
• move similar routines to a base class
• move non-similar routines to own PropertyHandler and ActionHandler

Further desirable activities

• Document them, including how to overload