TweetInfoPage: Handle Twitter errors more gracefully
Utils: Make show_error_object more robust

It now also works if the json stirng is malformed(in which case the
alternative will be shown).
Also, if the josn data does not contain an 'errors' array, but just an
'errors' string, we simply show that.
TweetUtils: Use show_error_object more often
Utils: Indicate that the error is an exception in show_error_object