systemui: move dock battery level views outside systemicons layout

At not the ideal, this at least will match normal battery level view, puttings battery levels
in the correct order. In addition fix two small dock battery bugs:
 -  BatteryLevelTextView not displayed if mode is TEXT
 -  Properly hide DockBatteryMetterView for modes NONE and TEXT
 -  Underline the dock BatteryLevelTextView to differentiate normal from dock text view

Screenshot: https://cloud.ruesga.com/f/74fe240c66/



Change-Id: Idfd3a4bb2f19bd29f9f4dd2b0ea7f645bb531986
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>