Improved object and tracker fiducial registration UI

[Rakhesis]

New class for creating fiducial buttons and keeping track of which button to set next: used to reimplement fiducial buttons for object and tracker.

Object fiducials:

• Register fiducials with a single click
• Colored buttons

Tracker fiducials:

• Changed fiducial registration order to left ear, nasion, right ear.
• Allow changing default fiducial registration order through constants.py.
• Allow setting fiducials outside default order.
• Improved code structure.

[vhosouza]

Thanks for the great PR. A couple of edits more:

In the Coil registration dialog:

1. Change the behavior of the dialog such that:

• If the tracker type is any of the Polhemus or if it's any of the Debug trackers: show the "Fixed" button and its coordinates and show the drop down menu of "Sensor 3" and Dynamic ref.
• For all other trackers (Claron, NDI, and Optitrack), hide the "Fixed" coordinate which corresponds to the current coordinate of the sensor 3 and collect this coordinate at the same time the button "Anterior" is pressed. This will reduce one click which is causing a lot of confusion to most of our users. Also Hide the "Dynamic ref" button which is not necessary.

2. Apply the same colors of the buttons to the 3D balls in the VTK scene of the coil.
3. Create a Reset button, similar to the one in the Tracker registration tab
4. Change all labels from "Stimulator" to "TMS coil"

In the Tracker registration tab:

1. Rename "Tracker" to "Patient"
2. There is a strange behavior after I have done the Patient registration once, if I click "Start patient registration" again it requires me to click "Reset" before starting the collection. I think this is a bit unintuitive. When clicking the "Start" button we should automatically reset the registration.

[vhosouza]

@Rakhesis I remember other tiny fix that can be added here.

In Image coregistration, after all 3 buttons have been recorded, disable the "Start registration". When it is kept enabled, it will also keep the "cross" enabled which prevents the use of other buttons, like measurement and brightness adjustment.

It's nearly impossible for the user to realize that the "Start registration" in the Image panel should be manually stopped.

[vhosouza]

In the Patient registration tab, the UI is still not updating in MacOS after the "Record fiducial" button is pressed. The UI is only updated after hiding and showing the tab again, or minimizing and maximizing the window. Some "Refresh" command is missing.

[vhosouza]

@rmatsuda

In this PR, @Rakhesis made a fix to hide the "Fixed" coordinate for Polaris and Optitrack and record the necessary coordinate already with the other clicks. It also hides the dynamic and sensor icons for these specific trackers.

Could you test with your navigation setup there that all is working fine. I tested the basic UI and all is correct, except for a minor update issue in MacOS.

[rmatsuda]

Hey @vhosouza and @Rakhesis! I tested the navigation setup with polaris and its working fine. Thanks for the PR @Rakhesis