AP_ToshibaCAN: add support for Toshiba CAN ESC

[rmackay9]

This PR adds support for the Toshiba CAN ESCs and includes some changes from @OXINARF's KDECAN PR.

Manufacturer product page is here (including video) and here (Japanese only sorry)

This driver has been both bench tested and flight tested on a real vehicle. There are some known potential issues:

• We send 4 commands (unlock, motor bank1, 2 and 3) every iteration (i.e. 400hz on copter) which is perhaps a touch wasteful although each command is quite small (6 or 8 bytes) so maybe it doesn't matter
• We should probably send motor bank1 after 2 and 3 because apparently all ESCs adjust their time when the motorbank1 message arrives (whether they're in motorbank1 or not).
• If we are unable to send a motorbank we don't try sending any later banks which opens up the possibility of later banks being starved. Perhaps we should just keep trying to send the motor bank forever?
• There's no feedback from the ESCs (yet) but I hope to add this in a future PR.

Below are some relevant bits of the datasheet. The ESCs don't have a "discovery" feature. Instead the user toggles some dip switches to tell each ESC what it's number is.

[tridge]

should this go in before or after KDE CAN ?

Txs for the help on this PR. I think I've addressed the issues found.

[rmackay9]

rebased and squashed. We will do one final flight test tomorrow that everything is still working OK.

[rmackay9]

This is rebased on master (which includes the KDECAN changes) and has also been tested on a real vehicle and confirmed to work so I'll merge shortly...

[tridge]

looks good!