Renamed membership-app widget to something more sensible.

Ryan, please take a look at the form-building Java in this area. I'm doing something wrong, but it's hard to tell what without being able to build and see errors. 

I've kept the Composite ```membershipYearComposite``` for its label, but I'm adding the two SELECT widgets __after__ it (rather than inside) to have more control over label placement and layout. But for some reason, DSpace just spills message IDs to the page and no widgets appear. Thoughts?