(PDB-798) Add capability to use regexp when querying fact-nodes path types

This adds the new operator ~> which is a path regexp operator that only works
against the `path` type. It works by internally converting the array of
regular expressions into a single regular expression for querying
fact paths.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #1037 from kbarber/ticket/master/pdb-798-regexp-for-fact-node-paths

(PDB-798) Add capability to use regexp when querying fact-nodes path types
(PDB-718) Fact path endpoint

This implements a "fact-paths" endpoint that returns list of fact paths/types
according to the specification here:
https://docs.google.com/a/puppetlabs.com/document/d/1vWE6tBmsPmMIYKQWV8Pwes_NIR9lEMTYjUH8zJ_AlMI/edit?pli=1