Add support for phriction.content.search and phriction.document.search

[tsimonq2]

These are going to eventually replace phriction.info and phriction.history. They're marked as "frozen" already on the master clone, so we should have at least have support for the replacements.

[goddenrich]

if you use

from phabricator import Phabricator
phab = Phabricator()
phab.update_interfaces()

then you should be able to do:

phab.content.search()
phab.phriction.document.search()

just fine