Rename pot2json.py -> po2json.py

The "pot2json" name was misleading; this script is really intended for
use *after* translations have been fleshed out (e.g. when you have a
LANGCODE.po file, for any value of LANGCODE) rather than when you have
an as-yet-untranslated app.pot file. (If the .pot file should be
converted to some other format, that might as well happen inside the
extract-translation-ids.py script, as the .pot file is being created.)
Merge branch 'localization'

One commit (renaming pot2json.py to po2json.py) had not been merged
earlier, but there was no reason for this.
build: refactor test-e2e to ensure setup is performed by correct user.

- root runs commands via build-lf.xml
- www-data runs php scripts
- shell is no longer called by php setup / teardown scripts
fix unlink exception in the wrong place
build: Fix the replaceregexp that was mangling our Thai examples in the e2e tests.
Merge remote-tracking branch 'lf/master' into feature/fileupload