Add single key F6 to toggle all panels of the editor, make F7 and F8 able to be used for other features later on

**Is your feature request related to a problem? Please describe (REQUIRED):**
I feel like it is a waste having these all as F keys in the editor, IMO there should be 1 key that toggles all three on and off, and then the other two F keys can be reserved for some other functionality down the road, and then have other shortcuts for toggling specific panels. What do other think about this?

It is far more common for me to want to close/hide all 3 panels at once to get as much screen for the code editor. I suspect this is similar for others too.

Double clicking the title of a tab in the main viewport should also toggle all 3. This is something we got for free in Editor 1 that I still miss.

**Describe the solution you'd like (REQUIRED):**
* Make F6 toggle all three panels.
* Move the shortcuts to toggle other individual panels to be other shortcuts. Save F7 and F8 for bigger features.
* Make double clicking the title of a tab to also toggle hide/show of all panels
* If user has selectively hidden a panel maybe only toggle the panels they last had visible.