Display: Default SRE to off

Facemelt mode is catching people by surprise and being interpreted
as "messed up colors". Default it to off so people can at least see
it kick in as a reaction to enablement

Change-Id: I5816e528363f508fc360c321c702a59f0bb79846
Settings: set proper default value for tap to wake

The first time the display_settings.xml file gets inflated, the
PreferenceManager takes the defaultValue and persists it in the default
shared preferences file.

When we read the double tap to wake preference,
we assume it has a default value of true, which it uses until the user
enters Display Settings for the first time. At that point, the default
value is persisted, and every boot after will use the default value in
display_settings.xml.

Remove the default defined in the XML file.

Change-Id: I0989dd73b6b3c42ff8649bc17eebf4e191293ee4
Signed-off-by: Roman Birg <roman@cyngn.com>