Make space navigator work on Windows

[Tom Goddard]

Currently space navigator does not work on Windows because the comtypes Python module is not included in the distribution.

[Tom Goddard]

I've added comtypes to the ChimeraX build. Needs testing.

[Tom Goddard]

Space navigator motion is working on a Windows 7 machine (viz vault boxx machine). But the two buttons don't recenter and switch to rotate+translate simultaneously. Those buttons work on Mac. On Windows the buttons need to be reassigned to "Application Use" instead of the default that brings up some 3Dconnexion controls. But that does not fix it. Probably the button names being received on Windows are not what we expect (although the Chimera 1 space navigator code is the same and works on the same machine in Chimera 1.10.2 -- couldn't test Chimera 1.11.2 because it won't start due to OpenGL not getting a visual).

[Tom Goddard]

I see Chimera 1.11.2 allow button names Left and Right -- that must be what it gets on Windows. Added that code. Needs testing.

[Tom Goddard]

Buttons working on Windows now.