License options on the advanced search form

[alexlittle]

Revise to be able to select from the by/sa/nc/nd options instead.

Feedback from user:
Do you expect your end-users to know or care about the difference between Public Domain and a Creative Commons 2.0 vs. 3.0 license? I get why you have these as fields for resource submission, but it seems like an odd use case for a community health worker to be searching for a particular kind of license.