face: Implementing InterestFilter abstraction to be used with setInterestFilter

This commit minimally changes the API, primarily altering the internal
structures preparing for separation of `registerPrefix` (=send a command
to local forwarder to register FIB/RIB entry) and `setInterestFilter`
(=update library's InterestFilter->Callback dispatch table).

The existing setInterestFilter methods preserve all previous functionality
(any string URI or ndn::Name can be supplied as a first parameter),
but also allow InterestFilter as the filtering parameter.
InterestFilter, provides a way to select Interest either based on prefix,
as before, or based on prefix and regular expression.

Change-Id: Id71404f2163f82c261018d21db172111c4b0da69
Refs: #1275