v0.5.1

Added

• Rename user slots without touching their sound: Device::rename_user_amp(slot, name) and
  Device::rename_user_ir(slot, name) (Python too) send only the import's name record (the AMP slot-info write,
  the IR 0x09 name write) and re-read the slot. The official app can't rename; confirmed on the pedal (a slot's
  sweep response before and after differs by at most 0.09 dB, rig noise; docs/05, "Renaming a slot"). Names are cut
  to 31 characters.

Changed

• The activity event for a user AMP slot-info write is "User AMP slot" (it was "User AMP import"), since a rename
  sends the same record; like "User IR slot".
• README and docs site: the NAM and IR graphs re-measured on hardware in one session with the official app's, 0.4's
  and 0.5's conversions (tools/pedalsim/readme_plots.py <session>, now with a dry-take reference instead of the
  Mac rig's calibration); the real-playing comparison is on the README and the site's front page.