When adding a new layer or map, the previous folder should be opened

[hm]

When you add a new layer or add a layer to a map, it would be nice if the previous folder used were opened as default. Also when you save a feature source, the "current folder" should be updated. When you later add a new layer and need to select the feature source the application should put you in that folder (where you saved the feature source) as default.

[jng]

Maestro already sort of does this, but the logic is sporadic and all over the place. We'll clean this up by putting the "remember last folder" logic inside the Resource Picker itself.

[jng]

Fixed r6490

[hm]

Please backport this to 4.0 branch

[jng]

Backported r6496