"Import Module" should add a @Folder annotation

[retailcoder]

ref. #3332

When right-clicking a folder in the CE and selecting "import", the imported module gets imported under the default folder unless it already has a @Folder annotation, in which case it gets added to whatever folder that annotation is specifying... which may or may not make sense in the current project.

Let's make the "import" functionality edit any existing @Folder annotation to match the selected CE folder, or add one such annotation when there's none.

[bclothier]

Closing this in favor of #1777 - track the issue there.

[mansellan]

Reopening, #1777 was for Project Explorer not Code Explorer.