This adds a 60 second screen timeout for TWRP. Might consider making this configurable in the future.
Will also set overlay to lockscreen so we don't have inadvetent screen selections.
Touching the screen will bring the display back up.
add back check script for poweroff
move diff time function to twrp-functions.cpp
make sure we chmod after copy_file
add read_file and write_file functions to twrp-functions.cpp
make single thread
try to force update screen
add forceRender
drop caches after tar processing

Change-Id: I3c5c509dd39dbb05451bbfe5d8b56d53c90d8d1b