Move locale-specific resources to "export_layers/locale"

These resources can be used by translators, hence their inclusion in the package.
Update Readme for Translators.md
Don't set default strip mode if file extension mode is changed

This is because the setting was always overwritten by its default value and thus did not remember the last used value.
Update CHANGELOG.md
Update instructions and formatting
Cleanup
Remove existing .pot files before generating a new one