webfaf2: set WSGIOptimization 1

This disables __debug__ and makes openid work on RHEL7.
webfaf2: remove arch field from summary.index

We don't have enough data in the DB to provide this type of filtering.
webfaf2: add dynamic creation of multiselect to improve page loading time
webfaf2: change default pagination limit to 40 (from 20)
webfaf2: only show BT diff form if problem has >1 reports
Merge pull request #301 from abrt/webfaf2_tweaks

Webfaf2 tweaks