Get path to current project with Tiled API

[solerante]

Is your feature request related to a problem? Please describe.
I would like to fetch the current project's path using the Tiled API.

Describe the solution you'd like
Something like tiled.activeProject which returns the path of the current open project.

Describe alternatives you've considered

• Asking the user the path of the current project.
• Putting the path in tiled.activeProject.path if there is some reason to make it an object. Maybe to dynamically make projects?

[eishiya]

I think this would be better as a comment on #2902 - Projects aren't accessible to the scripting API at all, and it would be better to have the path available as part of a proper API rather than just as a file path. The Project API should, of course, have a way to get the base path of the project, as well as the paths of directories added to it.

[bjorn]

I recently added this actually (462986c). I thought I might not get around to finishing the project API for 1.10 but at least wanted to provide access to the path, since it's most commonly needed.