Implemented transform skipping (for 4x4 blocks)

transform skip vs. normal transform selection criteria might need more work, currently both are calculated for each 4x4 block and SAD+coeff_SSE is compared.
Added 4x4 SATD (Hadamard)

Taken from HM 13.0
Added new commandline parameter --no-transform-skip
Changed final cost (and transform skip) error function from SAD to SSD