DOC: Move 'count' to the batch-bool 'Reducers' section of the docs.

[WarrenWeckesser]

count is in the doxygen group batch_reducers, and it shows up below the table of reduction operators along with reduce, reduce_add, etc., in the generated HTML, so it might as well be in the table.

Updated the PR so now count is moved to the 'Reducers' section of the batch-bool docs.

[serge-sans-paille]

count is a batch_bool only operator, it would be good to make that explicit, maybe by using two tables, one for batch and one for batch_bool ?

[WarrenWeckesser]

I don't know. I was originally looking for all and any reductions when I found this page and noticed that count was among the functions tagged as batch_reducers shown below the table but is not in the table.

I eventually found any and all in the Batch of conditions page. Perhaps count should be listed there.

[WarrenWeckesser]

Perhaps count should be listed there.

It looks like this can be done by moving count from the doxygen batch_reducers group to the batch_bool_reducers group. I'll undo my change to the table and make that group change instead. If I can figure out how to do a cross-reference with doxygen/sphinx, I'll add a "See also" note to the Reduction operations page.

[WarrenWeckesser]

I pushed a new update. Now count will show up in the 'Reducers' section of the batch-bool docs. I also added a note in the 'Reduction operators' page (where count used to show up) that links to the batch-bool 'Reducers' docs.

[serge-sans-paille]

Looks good, thanks!