p5100: Device makefile cleanup

-Removes the redundant full_p5100
-Standardizes the layout of omni_p5100
-add readme
-enableScreenrecordChord removed from common-overlay
 because it is set to "true" by default
-add vendorsetup.sh
-Updates the fingerprint to P5100XXDNA1 (4.2.2 Stock)

Change-Id: Ibc77306851738cd23407828956369619c5ca00fe