Open project in explorer

Hi!

Many times when I'm interacting with a Untiy project, I might not want to open it in the editor, but instead look at it's files, to eg. run a build or send it somewhere. It would be really convenient if the drop-down next to projects had an "Open in Explorer/Finder" button in addition to the Open with and Open with preferred buttons.

Similarly, the installs could have the same thing, as well as an "open template folder" for opening the folder containing the new MonoBehaviour template.