Furnace v0.5.7 (beta) - misc fixes and additions

this release brings the following changes:

• fix a crash when a custom font fails to load
• 1.1 .dmf support
  • as of now .dmf files saved in "save as..." are saved to this format version
  • a separate option exists to save in the 1.0/legacy format. this allows you to downgrade .dmf files.
  • currently the SMS+OPLL system is split in two chips, and the OPLL chip isn't emulated yet (wait for 0.6)
  • pattern names seem to work
• fix an issue which loaded some .dmw files incorrectly
• ability to rename patterns (click on the ++ at the top left corner of the pattern view to switch modes)
• make the visualizer no longer a secret! (right click ++ to toggle it)
• support for loading .vgi and .tfi instruments
• add a register view
• changes to arp macro view:
  • now a block instead of histogram
  • +0 reference line
• more demo songs!
• NES changes:
  • fix triangle being out of tune in higher octaves
  • better channel muting
• OPN: apply max frequency limit
• increase maximum octave
• Game Boy changes:
  • fix sweep in non-sweep channel messing things up
  • hide volume macro as it is unused
• fix E1xy/E2xy behaving wrong with arps
• fix E000 being treated too literally and perma-stopping arpeggio
• new compatibility flag: ignore duplicate slides (on by default for .dmf)
• allow changing note input keybinds
• add a seizure warning to the "about screen party time" option
• make about page animation frame rate-independent (thanks @franciscod!)
• PCE: LFO emulation fixes (hopefully it is better now, but still has to be determined)
• prevent layout screw-up when closing Furnace too fast
• fix bugged notes when loading some .dmf files
• more technical technical names
• fix some RtMidi compilation problems
• fix an issue when playing orders (replay keyOn in active channels during forceIns)
• several C64 fixes (particularly mute bypass fixes)
• fix playSub strategy which didn't handle post-loop cases (this fixes #174)
• fix deep clone giving false-positive warnings when muting channels
• fix hang when exporting to VGM with song end effect
• fix hang when rendering to audio file with "repeat pattern" turned on
• fix hang/memory munch when hiding channels with the visualizer on
• fix oscilloscope overflowing the window when its title bar is visible
• fix clipboard paste sometimes eating effect columns
• finally fix the pattern channel header color leak issue
• update credits

this is most likely the final release in the 0.5 series, unless any critical issue arises. prepare for 0.6!
thanks to everyone for your feedback!