Gamma Telecom Ltd. APNs added to sample config

We have added 4 new Gamma-specific entries to the sample APN config file

Test: Change added to LGE (hammerhead) device APN file
Test: built with make -j16
Test: Flashed onto a Nexus 5
Test: Gamma SIM inserted - after a while, Gamma APN settings were automatically applied

Change-Id: Ifa20f77104853655a2edeee43fd6c430fbf2d93a
Signed-off-by: Gamma Mobile Development <mobiledevelopers@gamma.co.uk>