west build: display closest matching board names on error

This commit modifies the 'west build' command to display the closest
matching boards when an invalid board is specified, making it easier
for users to find a typo in the used board name.

The user is also instructed to run 'west boards' if he wants to get
the full list of available boards.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>