Add simple safer actions

Actually 3 things:
1.  Simple safer query actions allow for easily rejecting or degrading
queries based on type rather than any complex rules.  Thus, simple.  The
only query types supported thus far are term_range and numeric_range.
2.  Documentation on how to integrate other plugins with this plugin.  Fancy.
3.  Add term_range and numeric_range queries to the list of known queries
to noop.  This should allow them to be wrapped in ```safer``` without forcing
the users to specify ```"error_on_unknown": false```.

Change-Id: I6d952db228212734a8bb20715219fc0d3663f019