healthd: Add dock battery support

Dock battery patchset chain:
base: http://review.cyanogenmod.org/#/c/55349/
native: http://review.cyanogenmod.org/#/c/55028/
healthd: http://review.cyanogenmod.org/#/c/55029/
settings: http://review.cyanogenmod.org/#/c/55212/
tf700t: http://review.cyanogenmod.org/#/c/55030/

Video (battery styles): https://www.dropbox.com/s/a7dp3glb7lv1zcg/dock_sdcard01.mp4
Screenshots:
 * No dock: https://www.dropbox.com/s/2yvngdaqok32xiz/dock_sdcard01.png?m=
 * No charging: https://www.dropbox.com/s/ezghtgoedei17oj/dock_sdcard02.png?m=
 * Docked no charging: https://www.dropbox.com/s/7fasc05fw5ylfxi/dock_sdcard03.png?m=
 * Docked charging: https://www.dropbox.com/s/x37vrhxzd075f7p/dock_sdcard04.png?m=

Change-Id: I5541af5a44167d4a515649daffb6346c4967e884
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
init.rc: TCP Performance tuning
charger: Draw battery percentage over charger screen

Let user know the exact battery capacity.

Port from https://github.com/CyanogenMod/android_system_core/commit/f7e1ef2461121c1ebe7f1ef3ea25cca397e4c5ab

Change-Id: I841efe8fa516cbd565e06fc2bd640ce7e3030d0b