Investigate QCanBusFrame API improvements

Suggestions from mmutz:

• add a proper default ctor so that not every default construction
  copy-constructs a QByteArray, e.g. by removing the = 0 from the current one
  and adding type = DataFrame to the FrameType ctor.
• add more nothrow markers. when doing so, drop the redundant inline keywords
  and QCanBusFrame:: qualifcations.
• not all methods need to be or even should be inline; that includes the
  constructors, but not the the special member functions (except, maybe the
  default ctor), though, and the class as a whole should stay unexported.
• don't use bit fields, they produce bad code on at least gcc and have
  implementation-defined layout. do the shifting and masking yourself on a
  quint64. You might then steam that quint64 instead of individual fields.
• remove the 'reserved' field. As it currently is, you cannot use it anyway,
  because no ctor inits it, so it contains random garbage. (init to zero for now)
• TimeStamps should be passed by value
• Create a type for frame IDs instead of using quint32: "type-rich interfaces"
• since setPayload and the ctor are unconditional sinks for their QByteArray
  arguments, those arguments should be passed by value and be moved from.

These changes must be done before the first final release of the API in Qt 5.8. Qt 5.7 and Qt 5.6 are TP releases for this API.