Refactoring: introduce a function for better encapsulation
Extract trw export module

VikTrwLayer module is really huge.
Export seems a good feature-candidate for externalisation.

Signed-off-by: Guilhem Bonnefille <guilhem.bonnefille@gmail.com>
Extract a UI module for babel

Create a module to factorize some UI related code.

Signed-off-by: Guilhem Bonnefille <guilhem.bonnefille@gmail.com>
SF Feature#49: Export via GPSBabel

Allow to export data in all formats supported by gpsbabel.

Signed-off-by: Guilhem Bonnefille <guilhem.bonnefille@gmail.com>
Fix error handling at autogen.sh
Fix previous fix
[QA] Use actual type rather than a gpointer
Support using multiple Viking files with relative paths.

Always calculate the canonical form for file references internally,
 so that they are always accessible.
When saved the relative path will be calculated if necessary.

Thus on file opening there is no further need for changing the working directory.
Fix compiler warnings from Export via GPSBabel work
Add function to work out the visibility of an item considering all the items ancestor's visibilities.
Ensure highlight for a single track or waypoint is always shown on top.

Special drawing for the highlighted item(s) ensures it is on top in case of overlapping items.

Introduce a delete layer signal, that is used by the VikWindow to help in preventing the attempt to draw a highlight of a deleted thing.
Fix another compiler warning from the Export via GPSBabel work