Handle a single carelink basal rate better

@jebeck @jh-bate @kentquirk 

These are the changes to handle a single carelink schedule better.  I tested not only via the unit test, but by pulling the offending data down locally and running it.  It is working.
A significant chunk of stuff will have to be rewritten with the new data model and the change of programming language, so I wouldn't rush to make too many changes to sundial based on server-side code like this.