Major refactoring on message types and addition of config commands.

• BREAKING: Removed factor and offset from diagnostic requests to minimize the number of
  fields, and since this is such an uncommon use case and one that can be
  handled by the client receiving the data. We may add them back in the future.
• BREAKING: Require an 'action' to diagnostic request commands, e.g. cancel or add.
• BREAKING: Rename "raw" messages to the more precise "CAN messages".
• BREAKING: Rename "translated" messages to "simple messages".
• BREAKING: Remove redundant type field from simple messages (formerly
  translated messages). The type can be inferred implicitly through the types of
  the value and event fields.
• Feature: Add a command for controlling CAN message passthrough.
• Feature: Add a command for controlling CAN controller acceptance filter bypass.
• Feature: Add a command to change the payload format.
• Feature: Add a command to control whether pre-defined, recurring OBD-II
  requests are enabled.
• Improvement: Add extras field to JSON messages.
• Improvement: Add an optional 'status' field to all command responses.
• Improvement: Build protobuf generated files with nanopb v0.3.1.
• Improvement: Allow explicitly setting CAN message frame format (i.e. standard
  or extended frame).
• Fix: Expand range of mode field to a full byte (#10)