Fix Tacx Fortius Device Support

Multiple fixups for Tacx Support -- as a result the support
is now pencilled in for full support in 3.0 SP1.

Fixes #24.
More Fortius Fixes

Including:
   * Fixed a type with slope mode updating the wrong byte array
   * Transposed bytes in the definition of the erg and slope messages
   * Added power smoothing

Note:
   It appears the Fortius is supplying torque not power, some more
   testing is being performed but expect to see an update shortly
   once this has been fully tested.