Get rid of language specific ftl files

[chenejac]

ftl files with hard-coded chunks of text should be redesign to use label keys.

Find solution for syntax differences between languages that does not require template customization per language:

1. find problematic labels
2. decouple to parts in free marker templates
3. translate (English translation of label key is mandatory, for other languages will be added by native speakers)

Tasks (reported issues which should be checked)

• [x] #2923
• [x] #2921
• [x] #3475
• [x] #3146
• [x] #3154
• [x] #3175
• [x] #3176
• [x] #3376
• [x] #3384
• [x] #2243
• [x] #2982
• [x] #3042
• [x] #3541