This reverts commit 22c6b619.

Clean up code and properly track number and position of active
reference pictures

Resolves crash in master branch

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);

Issue was introduced in !2587

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