Enable Ctrl/Shift-Click to open folder in a new tab/window

When using a laptop (on any trackpad without a convenient middle click feature) opening a folder in a new tap requires to right click on the context menu and select the wanted action. This merge request implements the possibility to press the ctlr and shift key when opening a folder for opening it respectively in a new tab or a new window. This correspondence between the modifiers and the effects is the same used by Firefox and Chromium/Chrome when clicking on a link in order to give users a familiar functionality.

• With double-click to open the behavior is the one you can imagine: you need two clicks to open a folder so, with just one and the shift or ctrl modifier you can edit your current selection of items, while with two you can open the folder you're clicking on in a new window folder (if you double click on a folder while selecting multiple ones the current behavior is preserved, so only the clicked folder is opened)
• With single-click to open the current behavior is used, so no folder is opened, but only the selection is updated (it's still possible to use shift/ctrl+enter to open a folder in a new window/tab) The previous distinction doesn't effect the folder or places panel because they don't have selections.

Depends on: Add new signals and logic to handle open directories in new windows or tabs