fix russian translation

Without fix got exception:
`ValueError: plural forms expression could be dangerous`
Added options --exclude, --only to sync_templates

Accepts list of arguments. Each argument pattern to fnmatch
--only sets only dirs that be processed
--exclude excludes some dirs from processing

Example:
```bash
python manage.py sync_templates --exclude "*lib/python*/templates"
```
Will process only app templates without any templates from apps installed in virtualenv or system
If you have yours apps in `apps/` folder
```bash
python manage.py sync_templates --only "*lib/python*/templates"
```