gproject, geanyproj: update to the latest API
gproject: Add the "external directory" feature plus lots of other changes

* Added the "external directory" feature
* Automatic tag generation for projects with less than 5000 files (configurable)
* Follow active editor on by default
* Treat empty "file patterns" in project properties as * (everything)
* Lots of minor iprovements, bugfixes (and probably new bug introductions)