Sharing pending

Implement sharing pending state.

3 place:
1. in group aside
2. in group header
3. in group timeline entries above title


change action possibility:

1. from normal group to sharing pending group
2. from sharing pending group to normal group
3. from sharing pending group to forwarded group
4. from forwarded group to sharing pending group
5. from forwarded group to normal group
6. from sharing pending group to accepted group
7. from accepted group to sharing pending group
8. from accepted group to normal group
9. from sharing pending group to rejected group
10. from rejected group to sharing pending group
11. from rejected group to normal group