TPac: patron saved searches

TPac: patron saved searches

Adds a "Save Search" option on search results pages.  When clicked,
users are prompted to log in (if not already), then given a chance to
save the search.  Saving is done from within a new "Saved Searches" tab
in My Account, where users can also see/delete/execute existing saved
searches.  The saved search UI also provides an RSS link.

Currently, only searches that build a query-parser query are save-able.
This excludes MARC expert search, at least until it can be expressed as
a query-parser query.

For more easier additions of query_type in the future, this commit also
changes the query_type column from TEXT w/ constraint to ENUM, which is
simpler to add types to.

Signed-off-by: Bill Erickson <berick@esilibrary.com>