Extension updated for newer versions of slicer

[xskere]

This PR updates the extension to work with the newer versions of Slicer.

1. Fixes problem in build with vtkMRMLLookingGlassViewDisplayableManagerFactory and vtkSingleton.
2. SetCurrentRenderer call removed as it is not available anymore.
3. Fixes Renderer being nullptr when trying to connect to LookingGlass device.
4. When setting up LookingGlass connection makes the reference view the 3D by default.

[cpinter]

This is a draft PR that already makes the extension work with the same devices. We'll try it with the latest models of Looking Glass and keep working on the PR if needed.

[cpinter]

Update: the extension works on the latest Looking Glass Portrait Go, but the aspect ratio is not correct with the current VTK external module.
What is happening is that the LookingGlassVTKModule does not have the device settings for the newer Looking Glass devices in vtkLookingGlassInterface::GetSettingsByDevice.

We manually added the information for the the Looking Glass Portrait Go that we have, and it looks like this:

settingsByDevice["go_p"] = DeviceSettings("Looking Glass Go Portrait"",
4092, 4092, // QuiltSize
11, 6,     // QuiltTiles (11 columns x 6 rows)
0.5625    // AspectRatio (1440/2560)
);

If a device is not found in this list the settings will default to another of this settings, resulting in the imaging wrong aspect ratios being displayed.
I sent an email to the manufacturer hoping they can provide this info for all the new devices. Once we have that, the PR should be good to go.

[cpinter]

Superseded by #30