Make Fittings Panel 'b' (impact parameter) box "Lock"-able

[karenacollins]

The impact parameter ('b') text field should be made "Lock"-able by adding a checkbox inside the 'b' value panel. Maybe add the checkbox to the right of the 'b' text field so the it will nearly align with the other Lock checkboxes above. If b is locked, then the b text box should be editable, while inclination should be forced to the locked state, but unlike the normal inclination lock state, the inclination text box should be made not editable. In this mode, the inclination value will be automatically set to inclination = arccos (b /(a/r)). While the inclination will be locked (i.e. not fitted), it's value will depend on the value entered for b, and the fitted value of a/r (or the fixed value of a/r* if it is also locked).

[karenacollins]

The original description of the feature above was edited to the current state after thinking in more detail about how the new feature should work.

[karenacollins]

Implemented.