Adding single opening view and template, started attempt at breadcrumbs

Still needs some clean up, but works enough that Reust can start moving files around. If I have time I'll do some further clean up this afternoon.

*Edit*
The additional commits added into this PR are mostly clean up of various loose ends, but there is one potentially controversial point I wanted to mention. 

After staring at the front-end for hours, I think the term "Commitment" for a Volunteer Commitment is awkward and a bit harsh. So I changed it to "Scheduled Visits" (only on the front-end and in the URL structure), which I think actually communicates the point more clearly, and focuses on the positive aspects of the activity. In any case, I can switch it back if necessary. Or, if preferred, I can switch the terminology all the way down to the DB, but that seems unnecessary to me.