Add a utility program nmfoffset that adjusts all time offset values of each note and all section offsets except for section zero by a positive number of quanta. This is needed for when the composition starts with a grace note, which can't be handled by the grace note compiler unless an offset is applied somewhere.

Add an nmfgrace utility program that operates on fixed-quanta NMF files and converts grace notes to actual notes with proper offset and duration, given the length of grace notes to use throughout the file.

NMF is no longer deprecated! Update the documentation to reflect this.

Add a utility program nmf2nrb that takes a NMF file with fixed quantum basis and no grace notes and converts it to an NRB file. This allows the new beta 0.5.3 architecture of Noir to drop all NMF support while maintaining backwards compatibility, because older NMF files can now be upconverted to the new NRB format using this libnmf library utilities.

This also allows us to use Noir beta version 0.5.2 and earlier with the new NRB rendering architecture, by simply upconverting the NMF results to NRB.

The only NRB features which are not available through the upconversion route are the Pedal and Grace flags in the articulation field, and the new ramp feature in NRB.

Move all (legacy) tool programs to the nmftools project, except for the nmfwalk utility program. Also move the tempo map documentation to the nmftools project.