Added vp10_fht4x4_sse2() unit test

Added vp10_fht4x4_sse2() unit test

Inherited class TransformTestBase to derived class VP10Trans4x4HT.
Employed RunCoeffCheck() to test vp10_fht4x4_sse2() against
C reference vp10_fht4x4_c().
fdst4_sse2() related seven hybrid transform cases are covered
 in this test.
Wrote a header file for test base class. Some modification to
make sure the base class can be used for 8x8, 16x16, 32x32 cases.
All related tests passed.

Change-Id: I6b19a39d3ea30b657847781e78e73b829998a57a