[ui polish] Add states (Download, Decrypt) to Files display

[ninavizz]

Add following states to existing display of Files w/in the client's conversation pane

• Updated Zeplin thingy
• Downloading
  • Needs to show while files are downloading to the machine from SD server(s)
• Decrypting
  • Should always show for a set timeframe; 2-3 seconds, I suspect?
  • Does not need to map to actual decryption time; point is just to regularly reinforce to users, that this happens.
• Opening
  • Should show immediately after user-action to open file has been triggered; just before disp-vm begins its launch.
  • Should revert to static/downloaded state as (tbd) seconds after invoking, to allow disp-vm to launch so user is not hopelessly confused.
  • Cursor should also change to show i-bar with sand-clock thingy icon for the same duration.
  • Point is to tell user "yo, something is happening!" until visual affordance of the new disp-vm window opens atop sd-svs vm pane

[eloquence]

We do have a Download spinner now. I somewhat question the value of separating out the Decryption stage, but this may become more important for larger downloads in the context of #1104.

[zenmonkeykstop]

Closing - we'll revisit the UX for files in the conversation view separately. The current implementation is a bit cluttered already.