hammerhead: add charging led support

Also introduces led priority handling for
battery vs notification vs attention
(copied from jf-common).

Requires the hammerhead kernel led
always on support patch.

Change-Id: I1a2f3aae457c6d7e4e3c3f9ca39cbe42d39c3bc2
hammerhead: remove apn copy step

Use World APNs file instead of default apn list from sample

Change-Id: I643efc70d8aa6482a2a4537dea67b2697307174c