[FIX] improves the search in runbot repo

now, it searches by fields 'dest' and 'subject'.  Also, slightly
improves the logic behind the controller.  Oh, and also prevent a
crash when searching
[IMP] optimize the number of queries in controller

now, it only does one query to get the ids of each builds,
instead of a query for each branch
[FIX] notifies github when duplicate isn't pending

when a duplicate build is created, it now check if it isn't pending.
If not, it properly notifies github.
Merge pull request #25 from odoo/master-fixes-and-optimizations-ged

[FIX] runbot: fix build search, optimize query for main repo view, update github status for duplicate builds