docs/EEPROM: Add "Backpack name" header
docs/PBBP: Split out the unique identifier description into subsections

It previously was a single paragraph, which made quickly looking
something up harder.
docs/PBBP: Give hardware revision a major.minor format

This was already happening in practice, but apparently not actually
written down.
docs/EEPROM: Fix offsets in SPI descriptor
tools/eeprom: Fix encoding of minifloat values

Previously, the exponent value would be written to both the exponent and
significand fields, messing up all minifloat values.
tools/eeprom: Add --bitlash option

This allows generating a bitlash command to update the EEPROM.
docs/EEPROM: Reorder the descriptors

No actual changes were made
docs/EEPROM: Assign type bytes to all descriptors
tools/eeprom: Reorder descriptors to match specification
tools/eeprom: Update type bytes to match specification
firmware: Rename backpack.c to firmware.c
firmware: Remove diffdump target from Makefile
firmware: add clean target to Makefile
firmware: Add .PHONY to Makefile