Crash fixes, various small improvements

Closes #255 (closed)
Vastly improves (solves for Mastodon, much better for Pixelfed although a couple of repeated items remain) #219 (closed).
Fixes issue where the user's followers are shown instead of the relevant account
Update dependencies
Add album icon to post preview if the post is an album
Remove unneeded API call
Fix some crash issues reported via TraceDroid
Add error messages in case of network or other API errors (instead of infinite loading progressbar)
Closes #223 (closed)
When accounts don't have a display_name set, use username in the profile title bar, follow{s, wers} list, post title bar,...
Add basic poll support to prevent crashes with mastodon

• Put error messages in strings to make them translatable
• Make error messages contain an indication of what error actually happened
• #263 (closed)
• add error message to accounts
• include credit for red panda drawing somewhere (CC-BY license, https://thenounproject.com/search/?q=red+panda&i=2877785)