Drop duplicate database indexes

These duplicate indexes were found by the pt-duplicate-key-checker
tool in percona-toolkit.  Duplicate indexes waste space and slow down
the query planner.  Closes #835.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Merge pull request #427 from andersk/duplicate-indexes

Drop duplicate database indexes
rebase translations, update script to maybe extract more translations from js files (fuck you xgettext you piece of shit)
Merge from upstream