Open Context menu on click on whitespace

[exalate-issue-sync]

Currently, only right-clicks on OcTableFiles rows open a context menu.

As a user, I'd like to do a right-click somewhere in space or folder to open a contextmenu containing actions:

• Create new folder
• Paste selection (after cut/copy)
• Details (for current folder)

Maybe as a followup:

• Upload file/folder
• Create new file (needs sub menu, because the list of file types to create is long)

[kulmann]

cc @diocas @elizavetaRa since we talked about this two days ago. Happy to hear ideas of what else could be in the context menu when clicking on whitespace in the files app.