AP_Scripting: Add filtering of incoming CAN frames

[EosBandi]

Add filters to the CAN buffer; mask is bitwise ANDed with the frame ID and compared to value. If not match, frame is not put to the receiving buffer
-- By default, no filters are added, and all frames are buffered, writing is not affected by filters
-- Maximum number of filters is 8 per buffer.
-- You can open as many buffers per driver as you want (every get_device() call creates a new buffer)

Usage : - driver:add_filter(mask, value) add a generic filted
- driver:add_DroneCAN_filter(message ID) to add filter for a DroneCan message.

Peter Hall rewrote my original version to a fully configurable, multi-buffer filter, so it is basically his code...

Use cases:

On a shared bus non-handled frames can be filtered out, making processing relevant frames easier and requiring less buffer and slower script update.
Can add script driver for composite DroneCAN devices with custom or experimental messages without the need for processing the frames that a non-script driver already handles. (Processing a single 1Hz custom message from a GPS/MAG device with maximum buffer size requires 5ms update time without filtering. A slower update or smaller buffer causes drop of messages)

[IamPete1]

I used sizeof when I should have used ARRAY_SIZE.

fixed

[tridge]

nice idea!
I'll wait for @IamPete1 to approve, this is really his area