Add "Open File Location" option to right-click menu in My Samples browser

[ttepatti]

Enhancement Summary

An additional button should be added when right-clicking a sample or folder containing samples in the "My Samples" browser, allowing users to open the file or folder's location in their system's file browser.

Justification

This makes it easy to locate sample files on your system from within LMMS if you need to edit, delete, rename, or otherwise modify your samples.

Mockup

This screenshot is from FL Studio, but displays the functionality.

[michaelgregorius]

#5454 implements a first solution which opens the folder that contains the selected file. It looks like this: