Port over Tap-to-Place feature from HoloToolkit

[lukastoenneMS]

Describe the problem

HoloToolkit has a Tap-to-Place feature that is missing in MRTK: https://github.com/microsoft/MixedRealityToolkit-Unity/blob/htk_release/Assets/HoloToolkit/SpatialMapping/Scripts/TapToPlace.cs

Describe the solution you'd like

Reimplement the Tap-to-Place feature in MRTK.

[DrewLovejoy]

Not sure if this is helpful to anyone, but I figured out a decent work around until this script is available. I used the "Interactable" script and the "Orbital" solver components.

I then did a little bit of configuring to make it work how I want it to:

• I set up the interactable component to be a toggle button by changing the dimensions to equal 2.
• I then selected the "InteractableOnToggleReceiver" Event Type.
• Then I created a script that has two methods, one that turns on the solver and one that turns off the solver. (This is pretty easy, just get a reference to the "SolverHandler" and then change the boolean "UpdateSolvers" to true or false.)
• On the "OnSelect()", I have it set up to call the method that turns on the solver.
• On the "On Deselect()", I have it set up to call the method that turns off the solver.