Add minimalegl QPA platform plugin

Add minimalegl QPA platform plugin

The EGLFS platform plugin was originally meant to be an example
and thus to be kept simple. However, EGLFS is becoming more
and more complex with the addition of hooks for board support,
cursor integration, built-in evdev support etc.

minimalegl is a new platform plugin that intends to follow
the original intentions of EGLFS.

The code is an adaptation of EGLFS as of f913859f8

Change-Id: I3d4cf84cde380cdcc7e0e8bfefff4df6be731b8d
Reviewed-by: Jørgen Lind <jorgen.lind@nokia.com>