Introducing option to choose methods for bayes_factor calculation

[vp35-illinois-edu]

1. Renamed bayes factor 1 to bayes factor using draw and test method
2. Renamed bayes factor 2 to bayes factor using gibbs sampler method
3. Introduced drop-down in UI to switch
4. Pending - May need to update "qtest_version" at Line 2115. Planning to do it in the next PR.

The UI now looks like this with a drop-down for Bayes factor under "Type of test."

[Emily-Line-UIUC]

Overall looks good - we should talk about the draw size arguments for the draw and test method. I'm assuming that it's using the same input values as the Gibbs algorithm, but the GUI draw size label should be changed to something more generic in that case.

[vp35-illinois-edu]

Overall looks good - we should talk about the draw size arguments for the draw and test method. I'm assuming that it's using the same input values as the Gibbs algorithm, but the GUI draw size label should be changed to something more generic in that case.

Can I remove the word "Gibbs" from UI and make it just Sampling?