Generic KeyValueTree broadcast

Generic KeyValueTree broadcast

Broadcast the KeyValueTree as part of inputrec, instead of having
special code in each module and a method in IInputRecExtension for this
purpose.  Now the only thing the electric field code needs to do for mdp
input/inputrec is to declare the options it accepts (and how they map
from mdp options).

Change-Id: Ia40120d4dd887c533cb6fcb60535852436dbd781