"Open with" menu when middle-clicking on files

[livanh]

A middle-click on a directory opens it in a new tab, but a middle-click on any other file currently does nothing. I find it convenient to use it as a shortcut for the "open with" menu. Currently only works for the GTK version. If there is interest in merging, i could look into QT as well.

[LStranger]

Thank you very much. Will consider it for version 1.4.0.