- Introduce a new D_xy tag which takes x_source and y_source
 - The two sources are attached to a DataConsistentcyGroup. Only If the
   consistency group signalizes a consistent state, the data is updated

The change in test application causes FROM_DEVICE values to be written
only if the TO_DEVICE variables are modified.

Fixes #21

Fixes #21

It basically decorated the AutoPropertyDescription with the type which
is now in AutpPropertyDescription

Helps debugging a bit

Parse "type" attribute for normal properties

Bubble up the type to the parent class

- Make doxygen pick up markdown.
- introduced: set_default_build_to_release.cmake

set_default_build_type_to_release.cmake -> set_default_build_to_release.cmake

'*.md' files put into the projects doc directory will be picked as part of
the documentation. '*.md' files in other locations of the source tree will
be ignored.

This closes #19