Reports: Ability to filter by 'number of attendances' rather than percentage

[tbar0970]

From https://github.com/tbar0970/jethro-pmm/issues/897#issuecomment-1522779859

Currently a person report can filter by attendance rate being more/less than X%. Percentages are based on them being marked P or A. (? is ignored). In some cases people don't use A - they just leave everyone blank except when they come.

It would be useful for person reports to be able to handle this.

I think the best interface would be:

Whose attendance at [▼ select cong/group]
has been [▼ more/less] than [ X ] [▼ percent / times present]
in the last [ Y ] weeks.

[tim-pearce]

I have implemented this in my system, except that I have currently made them two separate options. I should be able to modify it to be like you suggest. What you suggest is what I would have preferred but I was in a bit of a hurry at the time.