QS: Fix handling of dialer checks

Fixes an issue with network tile. Previously, if SystemUI crashed the network
mode tile would be disabled per the dialer check because constructor initialized
mUsesAospDialer to false.  Now we initialize it to the value of the system setting
and set it to 0 on shutdown.

Corrects display of disabled when the user has google dialer installed. Before,
the rssiTile would default to unknown.  Now it checks if google dialer is being
used and properly sets the disabled string.

PS1: Initial implement
PS2: Fix indents
PS3: Refactor content resolver
PS4: Update commit message
PS5: Style fixes

Signed-off-by: Evan Anderson <evan@thelinuxman.us>
Change-Id: I75cd767667924762fa432c29192674ce9c402c20
Merge "QS: Fix handling of dialer checks" into kitkat