Update for app framework removal

Update for app framework removal

Changes:
- Remove the autobuild scripts and config.xml used by the app
  framework widget build.
- Update the CMake files to just build a "xdg-cluster-receiver"
  binary and install it into /usr/bin by default.
- Bumped agl-compositor protocols version requirement to 0.0.20 to
  work with current AGL.
- Remove the code in main.cpp that handled reading the WebSocket
  command-line arguments and passing them to binding related
  code.

Bug-AGL: SPEC-4283

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I8c9bd3af9ce16f29f24282b89985c0d4d5d9c922