Allow customization of charger animation

Allow the charging animation to be customized with a configuration file
and custom assets.

 - Add a parser to parse a custom configuration file.
 - Add support for showing a clock and the battery percentage.
 - Expand feature that conditionally shows animation frames using min_level
   and level_only to min_level and max_level

BUG: 29547343
Change-Id: Ia33f4bb37dc7d4c7fa6507a63481e93bf0bf9738