Implements a couple simple tests of the encoder API using the gtest
framework:
TestDisableKeyframes
TestForceKeyframe
TestKeyframeMaxDistance
Change-Id: I38e93fe242fbeb30bb11b23ac12de8ddc291a28d
Rework unit tests to have a single executable rather than many, which
should avoid pollution of the visual studio project namespace, improve
build times, and make it easier to use the gtest test sharding system
when we get these going on the continuous build cluster.
Change-Id: If4c3e5d4b3515522869de6c89455c2a64697cca6