Verify apnContext is not null before it gets dereferenced

If this is still null a NPE will be thrown when it is dereferenced later on

Change-Id: I71ec478eb32425ca4242ee1eb366756648935350
DcTracker: verify preferred apn list is not empty before enabling

If a non-null but empty cursor is returned mCanSetPreferApn will be
set to true even though the preferred apn list is empty. Verify the
cursor contains at least one apn before setting mCanSetPreferApn.

Change-Id: I6a66ab334d997d8ced06ea0b596ba3463f4ce85b
DcTracker: respect build property for multiple data connections

Change-Id: I90094708a4ebf050837db3405f76c1875c3f42de
[3/3] Opt/Telephony: Add MobileNetwork Flip Tile

base from:

https://gerrit.paranoidandroid.co/457

with moarr changes to OmniRom

toggle Network Flip Tile

for device support 4G (GSM)
toggle will change into 2G only => 3G only => 2G/3G auto => 2G/3G pref => 4G lte => back to 2G only

for device support 4G (CDMA)
toggle will change into cdma/evdo auto => cdma only => evdo only => 4G lte => back to cdma/evdo auto

for device unsupport 4G (GSM)
toggle will change into 2G only => 3G only => 2G/3G auto => 2G/3G pref => back to 2G only

for device unsupport 4G (CDMA)
toogle will change into cdma/evdo auto => cdma only => evdo only => back to cdma/evdo auto

4G toggle requires that at least one (1) of the following configs
must be present in the device's build.prop in order to use it:
telephony.lteOnCdmaDevice=1
telephony.lteOnGsmDevice=1

Change-Id: I50950399537b19954a4f4fb19d038a07c8759c36