add feature to do preventative treatments and to treat whole herd.

I do a bi-yearly preventative coccidia treatment and it would be great to be notified when that needs to begin/end. but currently I have to enter an ailment, and a rabbit, in this case, and many others, there is no ailment, and I am going to treat the whole herd. it is very rare that I am going to do a treatment on less than the herd, and if I did I would not have a "plan", just try until the rabbit gets better or dies, so the current setup of the health is pretty useless.