CAN update fixes

I've been testing CAN firmware update with latest beta MissionPlanner. There are a few small improvements to MissionPlanner that would help a lot:
- when selecting the path to send in BeginFirmwareUpdate make the path short enough to fit in a single CAN frame. A name like "fwN" would be good where N increments. This helps a lot over SLCAN where CAN comms is not always fully reliable. By choosing a small path I've found it to be noticibly more reliable.
- when the CRCs match MP throws an error which looks like a failure to the user. When they click details they can see it is just a CRC match. Better to show a normal dialong instead of an error
- in file selection box allow for the drop down for "all files", as not all firmware may be called xx-crc.bin

Other nice features:
- it would be very nice to display the uavcan::protocol::debug_logmessage messages when in the slcan window. These can be used to display errors to the user
- for param fetch, displaying the params as they come in would be nice, given how long it takes

Start by tracing BeginFirmwareUpdate, the SLCAN window, the firmware file-selection control, and the parameter-fetch flow. Check how CRC matches are reported and how CAN paths, file filters, debug messages, and incoming parameters are displayed; done means these five requested improvements work without presenting a matching CRC as a failure.

Written by the indexing model from the issue text.