provide looser check of meeting pattern compliance

[rpruim]

We should probably allow meeting patterns that are a subset of an official meeting pattern to go through without flagging them, or at least have the option to do it that way.

This isn't urgent since most departments probably won't have that many sections that use only a subset of the days in their meeting pattern. But things like seminars will often fall into this category.

[rpruim]

This is being closed in favor of #300 which was easier to implement and probably more useful.