R1:99704ed48513

Support operators in Phabricator search

Summary:
Boolean search supports operators, such as phrase search.
It can be further improved by setting [[http://dev.mysql.com/doc/mysql/en/server-system-variables.html#sysvar_ft_boolean_syntax | 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…