set flag `read_in_gml` in `read_in_prj()` in vignettes

the flag read_in_gml is required when reading in a PRJ file via read_in_prj(). This is missing in the vignettes and examples.

changed milestone to %public version v0.2

added bugfix label

assigned to @joboog

mentioned in merge request !31 (merged)

mentioned in commit e0e9d6e6

closed with merge request !31 (merged)