v2.1.6 Program Changes and fixes

Changelog

• #72 (#71) adding program_change config option, that will insert Program tokens whenever an event is from a different track than the previous one. They mimic the MIDI ProgramChange messages. If this parameter is disabled (by default), a Program token will prepend each track programs (as done in previous versions);
• #72 MIDILike decoding optimized;
• #72 deduplicating overlapping pitch bends during preprocess;
• #72 tokenize_check_equals test method and more test cases;
• #75 and #76 (#73 and #74 by @Chunyuan-Li) Fixing time signature encoding / decoding Time Signature workflows for Bar/Position-based tokenizer (REMI, CPWord, Octuple, MMM;
• #76 Octuple is now tested with time signature disabled: as TimeSig tokens are only carried with notes, Octuple cannot accurately represent time signatures; as a result, if a Time Signature change occurs and that the following bar do not contain any note, the time will be shifted by one or multiple bars depending on the previous time signature numerator and time gap between the last and current note. We do not recommend to use Octuple with MIDIs with several time signature changes (at least numerator changes);
• #76 MMM tokenization workflow speedup.