Standardize use of getBus vs getBusId for CanMessage.

Fixed #161.
Add fractional seconds to timestamps on CAN and diag request views.
Add an Enabler view to send a CAN message.

Fixed #153.
List all previously sent messages in the "send CAN message" view.
Merge pull request #162 from openxc/send-can-message

Add a view to Enabler to send an arbitrary CAN message