Redo checkin page

[nharper]

UI changes:

• member-facing:
  • numpad takes up too much space - hide behind "forgot card" button
  • confirm manual entry
  • fix font issue on numpad backspace and enter buttons
  • only display one member at a time (and make name, photo, etc. larger)
  • better ui for errors
• admin:
  • add "admin" panel - for switching between checkin/checkout, uploading data, future features
  • some way to scroll through list of all data about to be submitted
  • better handling of updated appcache
  • loading indicator when saving things to appcache in background
  • better ui for errors (both member errors and errors from admin interaction, e.g. upload)
  • improve re-login flow

Improvements to make it more app-like:

• disable scrolling
• disable zoom (i.e. pinch to zoom)
• go fullscreen
• disable back button (probably not needed if we're fullscreen)
• prevent screen from sleeping (if possible)

Potential new features:

• load all rehearsals and ability to switch between which rehearsal is active
• automatically switch between checkin and checkout based on time

[nharper]

Here's a wireframe of what the re-done checkin page could look like.