Allow config of number of users shown on "Highest" blocks

Please allow a config setting to specify the number of users to show on the "Highest {category}" blocks.

Also, it would be nice to have an overall highest points block in addition to the "Highest {category}" ones.

One strange behavior I noticed, when I first enabled one of the "Highest {category}" blocks, it showed five users. I then changed the block title and, after saving the block, it then showed ten users - and it stayed at ten even after I went back and blanked the block title (to get it to use the default title again).

The two attached screenshots show the block before and after changing the block title. Both screenshots are from the admin user.