Minor refactoring of rendering and simulation manager

See merge request !244

Also enforces formatting

Also, move constructor of VTKViewer to .cpp

Use already defined enums as arguments

launchSimulation and startSimulation have similar meaninn to be included in public API.
Moved the launch simulation to be a private member.

ENH: shadows, bloom, shader options

See merge request !235

Integration of the Virtual Reality

See merge request !243

The simulation can now be set to either instantiate:
  - A regular simulation using vtkRenderWindow
  - A VR simulation using vtkOpenVRRenderWindow

To do so, the simulation manager can be set to be a VR simulation
when initialized. The default comportment will be a regular simulation.

BUG: Use proper writer for VTU file

See merge request !242

COMP: Allow build of projects depending on iMSTK updating the config file

See merge request !241

ENH: Add Orange color

See merge request !240

Suggested-by: Alexis Girault <alexis.girault@kitware.com>

This is needed for the VROrthognathic/OrthognathicTrainer project.

This commit adds missing dependencies to iMSTKConfig file.

Assimp was originally introduced in f859365b (ENH: Added Assimp support
to improve mesh reading)

glm became a mandatory dependency in 54a68c1f (ENH: added decals to the
Vulkan renderer)

COMP: Support build with BUILD_EXAMPLES and BUILD_TESTING set to OFF

See merge request !236

COMP: Update external projects to use CMAKE_CACHE_ARGS

See merge request !238

Unless option have to be passed using the command line, this is the
recommended approach to pass options. It avoids "command line length issues".

COMP: Fix compilation error in VulkanTextureDelegate

See merge request !233

Surface mesh fixes and decals

See merge request iMSTK/iMSTK!224

CLEANUP: added ability to expand surface meshes, abstracted interactor, and fixed transforms in Vulkan renderer

Changed to pass the shared_ptr by reference.

See merge request iMSTK/iMSTK!231

Add relaxation solvers

See merge request iMSTK/iMSTK!230

Simplifies graph printing format.