relay - several problems

[jontrulson]

• never sets the gpio direction

• does both reads and writes on the gpio... I'm don't think that will
  work reliably?

• is_relay_on/off() reads a value, but doesn't do anything with it. I
  changed to return the correct state, but again, the above two issues
  probably means this may not actually work and should be removed.

  Also, they should return a bool, but instead return a upm_result_t.

• Uses a switch FT, but a switch FT only gets a value, it never sets
  one, so it's kind of useless for a relay. Need a new output switch
  FT?