Merge branch 'release/v0.6.1' into develop
fix typo
split out history into ChangeLog.md file

ChangeLog might grow quite large, so better keep it separate from the
README
allow empty po files (no strings defined)

show a warning, to inform about this.
fix problem with trailing white-space in translated strings

trailing white-space have been removed, before. This is wrong, since
extracted strings should not be changed in any way.
bump version to 0.6.2
Merge branch 'release/v0.6.2'