…check

Tests for checking if RPC request and for constructing p4p Value obj.

Also now don't parse for RPC unless know its a valid request,
and now able to emit discon signal when polling.

And have the thread be killed if the pydm window closes.
Also now correctly have pollrate value as float.

Fixes issue where screen with many RPC widgets will stall
when loading if can't connect to addresses (such as when  not connected
to the network).

Since should work with any widget that expects back a value to display
(also works with byte-indicator widget)

…NTURI wrapping

…th no args

… when disconnected with the widgets