crowdin: Externalize user-specific configuration

This will generate a warning at the moment:
(Warning: Configuration file misses parameter `base_path` that defines your project root directory.)
since the user-specific configuration doesn't support base_path yet.

The script still works and uses 'pwd' as base_path

Change-Id: Ib684dcac79204a3f8f3b2c48c361b70b114dc745