Merge pull request #751 from houqp/new_ui_code

fix coordinate calculation for blitbuffer rotation
KUAL extensions added (since kindlepdfviewer will soon support all devices)
remove unrequired scripts
update to direct referencing of scripts.
SIDE-EFFECTS: this means /mnt/us/kindlepdfviewer/kpdf.sh is now the REQUIRED location as opposed to preferred.
add extensions directory in customupdate