Add failing unit test to demonstrate problem with text domain merging
Split up loading method into logical chunks
Provide fix for text domaing merging
Merge branch 'hotfix/3947'

Close #3947
Merge pull request #3948 from DASPRiD/bug/merging-translator-textdomains

Bug/merging translator textdomains
Merge branch 'hotfix/3948' into develop

Forward port #3948