Rename on double-click instead of click

[martinRenou]

This allows clicking on the entire bar (instead of just the icon) for collapsing directories. Which is the kind of UX that common IDEs provide.

[timkpaine]

relates to https://github.com/youngthejames/jupyterlab_filetree/pull/42#issuecomment-826374175 and https://github.com/youngthejames/jupyterlab_filetree/pull/38#issuecomment-826370381 but actually on Mac when you click on the folder name it does not expand the directories, you have to click on the tick to the side to do that. Double clicking on a folder generally moves you inside that folder (this is the behavior on both Mac and Windows).

[timkpaine]

Also double clicking on a file should open the file, not rename it. Doing a second single click on an already selected file should trigger the rename.