Add MultiROM config

Conflicts:
	BoardConfigCommon.mk
Enable BUILD_OLD_SYS_PROPS := true

* This is only in my build tree, not omnirom

Conflicts:
	BoardConfigCommon.mk
Correct mr_init_devices.c
Fix path to key input in mr_init_devices.c
Remove discontinued BUILD_OLD_SYS_PROPS properties

Conflicts:
	BoardConfigCommon.mk
Add MR_DPI_FONT
Add rom_info.txt for SailfishOS
Fixup TWRP config