Add all channels, groups and dms & Add styling changes

[tscritch]

Changes in this PR:

• allows the user to view all of the private groups, one-to-one direct messages, and multiple person direct messages.
  • styling changes were made for a more responsive and user friendly interface. It now has an appearance closer to slack
  • dropdown menus for each type of message group.
  • when going to a different page the sidebar will scroll to the position of that element in the list.
  • for the one-to-one direct messages, the extractor will save the list of dm ids that do not exist in the archive. This can then be used upon relaunch to filter out unused dm ids.

[hfaran]

Thanks for the patch!