add radio button widget for airborne fdem

[lheagy]

Images and radio buttons for airborne fdem basic physics.

@fourndo, @yangdikun : see what you think

[lheagy]

• [ ] prior to merging, the text for the widget should be updated (@lheagy)

[fourndo]

@lheagy I forgot about your branch and created another one: GeopSurvey_AFEM. Want to merge this in here?

[lheagy]

up to you! This is small, so we could easily merge it onto the branch you are working on

[fourndo]

Merged in, will continue the work on Geop survey afem #396