Idea: Propagate only changed translation files

[rffontenelle]

Currently, we are propagating latest version's translations of all translation files from all languages into all other versioned branches.

A more optimized solution would be to identify changed files and only run pomerge only for those languages, for all versioned branches. E.g. if only Chinese translated files in this week, propagate only Chinese's translations instead of all languages.

Looks like scripts/manage_versions.py would need to be adapted for this.