Initial rework to run without the app framework

Initial rework to run without the app framework

Changes:
- Remove application framework build scripts, and update the
  application qmake file to just build a "homescreen" binary
  and support installing it to /usr/bin.
- Remove voice API related code.  Some of the associated QML
  and images for the UI have been retained in case equivalent
  functionality is re-added in the future.
- Remove or stub out various app framework API access for the
  homescreen and launcher bindings, and comment out usage of
  the Qt wrappers from libqtappfw (e.g. Bluetooth).  The aim is
  to provide a replacement library or libraries for the latter
  that provide the same functionality.
- Remove the old homescreen API documentation and do an initial
  update of the build instructions in README.md.

Bug-AGL: SPEC-4121

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: Iab979c8e1341f2da0384f88f163a977b03664600