Allow to export layouts from sub-folders

[DelazJ]

Is your feature request related to a problem? Please describe.
We can export layouts from project files within a folder but not from projects in sub-folders.

Describe the solution you'd like
Add a checkbox to decide whether sub-directories should be included in folders to fetch the layouts from. A prototype is at master...folderRecursive

We should also consider how to manage the sub-directories projects output files location