Make sure pgAdmin support the menu button

[Ram Rachum]

I like using the wonderful menu button on my keyboard. This is the button in the lower-right area of the keyboard which causes a context menu to be shown. For example if focus is on a database and I press that key, it should raise the context menu.

Alas, it doesn't. Shift-F10 works, but not the menu key.

Here's a rule of thumb: Everywhere where you support right-clicking something to raise a context menu, you should support pressing the menu key.