In preparation for vendoring libjamiclient into 'src/libclient/'.

GitLab: #734
Change-Id: Ibd956abc8fe9bd454ac0e9a5a28b77a5a74174e7

Functionalities checklist:
  1. Emoji picker refinement
  2. DropArea on messageWebView
  3. Record box
  4. Send message button visibility
  5. TextArea paste (can paste image, files directly)
  6. TextArea content draft
  7. TextArea - Enter key -> Send message
  8. TextArea - Shift + Enter key -> New line
  9. TextArea - Composing indicator
  10. TextArea - Placeholder text

Change-Id: I115ad2927b74264dd396aa55b77a8f003dcd746b

1. New emoji picker by customizing emoji.js
2. New message bar ui (textarea, buttons, tooltips)
3. New pending files transfer container
4. Use MaterialToolTip for all PushButton

Change-Id: I05d0531c65c019ced42b04668a780919c8a4fac3