Remove all mostly untranslated PO files

We only import PO files that are at least 75 % translated,
so we can delete now all other PO files. The patch only
removes the mostly untranslated files. Once a file becomes mostly
translated, the bot will import it again.

This removes all languages besides en_US.

Change-Id: Ic6d9b36a04260a2dd2f605379b847e0165449ce8
Closes-Bug: #1317794
Use joins instead of subqueries for metadata filtering

Previously, Ceilometer used subqueries to apply metadata filters. These
subqueries, however, defeated MySQL's query optimizer, leading to absurdly
bad performance. In our production setup, this patch improved performance on
two metadata filters by up to 10000x.

Change-Id: Ie3bea14d05fb63a5565e2d5cced74068955b8f08
Closes-bug: #1320772
Merge "Remove all mostly untranslated PO files"