Hercules Inpulse 300: add toneplay, slicer, and beatmatch functionalities

[BoredGuy1]

Note: This adds some last-minute edge case handling to #14051, which is a squashed version of #12503 (sorry for the messy commit history).

Original description (edited a bit to reflect recent changes):
I made some improvements to Mixxx's included Inpulse 300 mapping. I tried to stay close to the manufacturer mappings listed in this manual.

Full list of changes:

• Added ability to stop samplers (shift + button)

• Added toneplay

  • Pressing a pad jumps to the most recently used hotcue and changes the pitch
  • Shift + toneplay changes the pitch without jumping
  • Pads 1-4 increase the pitch by +0 to +3 semitones
  • Pads 5-8 decrease the pitch by -4 to -1 semitones
  • LED reflects total adjustment to current key

• Added slicer/slicer loop:

  • Press slicer button to activate a slicer section, press again to deactivate it
  • Slicer length is dependent on loop length
  • Exiting slicer mode or pressing LOOP OUT also deactivates the slicer section
  • Creating a slicer section overrides active loops, and creating a 4-beat loop overrides active slicer sections
  • Only works on constant BPM (also true in native software DJUCED)
  • Slicer section does not move backwards when scratching (also true in native software DJUCED)

• Added actual beatmatch guide functionality to the LEDs

  • This replaces the LEDs' old end-of-track warning functionality. Hopefully no one missed it :P

• Changed the way scratching works

  • Wheels have inertia rather than instantly stopping when released (this allows backspins and other tricks)
  • Removed scratchPad in XML (not sure what it was doing there)

• Fixed some syntax

  • Replaced connectControl with makeConnection to allow multiple connections (and also to comply with newer versions)
  • Replaced "hotcue_X_enabled" with "hotcue_X_status" in XML file to comply with newer version of Mixxx

Manual is being updated accordingly in another PR: PR#604.