Update meson and cmake config to only include openrtx and platform paths.
Update files to use <..> for system and external libraries, ".." for
project files and new relative paths as necessary.
Did not attempt to fix areas where includes that should be <..> were
previously ".."
Inspired by #96, closes#359.
Acked-by: Silvano Seva <silseva@fastwebnet.it>
Ryan Turner
Silvano Seva