Updated FAQ Client section

Updated FAQ Client section

- improved intro text
- removed Metatext iOS client (never worked without errors for friendica)
- added Mastodon iOS client
- corrected link for iOS Stella
- updated Tooot link, added data collection hint
- Tootle: removed hint and added update year
- corrected Stella* name
- removed StarPterano (app not updated for a while, no privacy policy provided to apple, UI lacking, login on every open required - not a user experience to recommend)
- Sailfish Friendly: improved link, added last update year
- macOS added Whalebird
- updated german faq