Handle generating weston.ini in post-install script, based on deviceinfo options
This removed the weston.ini file and automatically creates it in the postmarketos-base post-install script based on options set in the deviceinfo file for a particular device. This replaces #191.
(Optional) options supported in this PR for deviceinfo are:
deviceinfo_weston_core_modules - defaults to NONE if none specified
deviceinfo_weston_core_backend - defaults to fbdev backend if none specified
deviceinfo_weston_keymap_rules - keymap rule, found under /usr/share/X11/xkb/rules/
deviceinfo_weston_keymap_model - keymap model