battery LED: nearly full level is now configurable

Nearly full level of battery was hardcoded as 90 in BatteryService code. With this change it is possible to adjust in via config.xml

Test: manual tests. It's possible to test in the emulator with additional logs. lunch sdk_phone_x86 && m && emulator => emulate battery changes
Signed-off-by: Artem Vursalov <artyomvoid@fb.com>
Change-Id: Id632424b5819fba2abe82b28af0f1993688db2e2