appDisplay: Make middle-click like Ctrl+click
When middle-clicking an app icon on the Dash, it will always try to open a new window of that app, even if the app doesn't support multiple windows. Meanwhile, Ctrl+click on an app will only open a new window if the app allows it.
This change prevents middle-clicks on app icons from opening new windows for apps without multi-window support.
Closes: #316 (closed)
Edited by Xavier Johnson