This reverts commit 22c6b619.

The proposal JVET-AE0057 is implemented under the define JVET_AE0057_MTT_ET in VTM software. A config file parameter (MTTSkipping) is also added to turn on or off the MTT early termination. The 64x64 luma CU no-split intra RD cost is compared against a threshold to decide whether to evaluate MTT splitting for current 64x64 luma CU.

m_nnPostFilterSEICharacteristicsPicWidthNumeratorMinus1 is renamed to m_nnPostFilterSEICharacteristicsPicWidthNumerator

m_cEncLib.setNNPostFilterSEICharacteristicsPicWidthNumeratorMinus1     (m_nnPostFilterSEICharacteristicsPicWidthNumeratorMinus1[i], i); is changed to m_cEncLib.setNNPostFilterSEICharacteristicsPicWidthNumeratorMinus1     (m_nnPostFilterSEICharacteristicsPicWidthNumerator[i] - 1, i);

The default values of sps_chroma_horizontal_collocated_flag and
sps_chroma_vertical_collocated_flag are modified to take on values according to
the specified chroma location type. If no chroma location type is specified,
the default values of the flags are as prior to this commit.

Implementation of AD0056 item 5, don't signal nnpfc_input_pic_output_flag[i] flags when nnpfc_num_input_pics_minus1==0 and infer nnpfc_input_pic_output_flag[0]=1 instead

Express frame rate as ratio of two integer values throughout code
using struct Fraction

Add support for defining fractional frame rate from command line