Support operators in Phabricator search

Summary:
Boolean search supports operators, such as phrase search.
It can be further improved by setting ft_boolean_syntax to ' |-><()~*:""&^' (note the leading space):
Default value uses no operator for "optional word" and + for "mandatory word".
This value uses no operator for "mandatory word" and | for "optional word".

Test Plan: Search for "Enter the name" (with quotes).

Reviewers: epriestley

Reviewed By: epriestley

CC: aran

Differential Revision: https://secure.phabricator.com/D2064