Change PRODUCT_MODEL to Desire Z

This avoids getting "HTC HTC Vision" in some places.
I agree that there are T-Mobile G2 users, but I don't
like to use carrier-branded name, nor keeping platform
"codename" as a device model.
Edit keylayout files

Change file modes in keylayout, they were
marked as executable for some reason...

keypad-wwe: edit comment for better explanation
BoardConfig: remove obsolete values
VisionKeypad: Update Persian keyboard mappings
VisionKeypad: replace app icon
VisionKeypad: change app_name to "Desire Z Keypad" for better consistency