message: doc: Clean up spec changelog
diff: - Adding StepCount to Message Attributes, to let users know how
  many steps a feature can use (i.e. how many vibration levels a
  piece of hardware might have)
  - - Adding PatternNames mapping to Message Attributes for anything that
  - supports PatternCmd.
  - ServerInfo
  - Remove Version fields
  - Messages Deprecated:
  - RotateCmd
  - Messages Changed:
  - DeviceList/DeviceAdded
  - - Added Message Attributes blocks to device info.
  + - Added Message Attributes blocks to device info, with FeatureCount attribute
  - RequestServerInfo
  - Added Spec Version Field
  - Messages Deprecated:
  