ipmi lan commands

IPMI endpoints for:

   * `ipmi lan info|set` at `/machines/:hostname/lan` and `/machines/:hostname/lan/:channel`

Stub endpoints for:

   * `ipmi sensor` at `/machines/:hostname/sensors`
   * `ipmi lan alert info|set` at `/machines/:hostname/lan/alert` and `/machines/:hostname/lan/:channel/alert`

The stubs can be filled in once we have patched pyIPMI with the required IPMI commands.