Add a simple Binding query language

Add a simple Binding query language

Offloading some amount of data matching towards the storage engine
can give use two-fold improvement:

1) skip instantiation of Binding DTOs, as the query can be realized
   in terms of DOM matches
2) potentially skip transfer of large amount of data

For Binding layer we want to have something type-safe, where we are
in control of the flow the language.

This provides a first cut at the structure, which may end up being
further evolved.

Change-Id: Ica52158c889c0df9a6004227c0b64092590f67af
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>