Start reafctoring plot curves
Update Travis CI before_install with GDAL
Refactor curves data fetching
Change group header

* Add "g" in group identifier in read_grp_curves
* Change "-" to "."
Refactoring curves data getters complete
Fix documentation
Renames tests, add utilities tests
Assign feature names to curves data
Add check_names() utility function
Assign group names to curves data
Add check_names and plot_curves to NAMESPACE
Update docs
Update vignettes
Add AllGenerics
Add plot_curves to Zresult's methods
Update docs
Fix featurenames signature for Zvariant
Fic Zcurves docs
Refactor generics from Zproject to AllGenerics
Move generics from Zresults to AllGenerics