Analyzer: Allow selecting top-level app content to create exclusions

[d4rken]

Via email:

With respect to Storage Analyser, if I select Storage Analyser | Storage Content | Apps select and an app (in the attached I selected Google Play Services) and then choose the second path /storage/emulated/0/Android/Data/com.google.android.gms and selected that, I get a pop-op that "no direct access available".

I can reproduce this in v1.4.1-beta0, top level items don't allow long-press to selection, so these can't be used to create exclusions. Don't see a reason why this shouldn't be made possible.

Also see #1644 and #1645