simpleNav replacement for genericNav

We've been encountering a few issues with single threading of "Query of Queries" on the Railo engine affecting performance on high traffic sites. This lead Daemonite Justin (@justincarter) to refactor the common <skin:genericNav> tag as it uses a few QofQ.

We've added the new <skin:simpleNav> to core (in branch p630+). It differs from <skin:genericNav> in a few ways:

At this time it's not intended as a full blown <skin:genericNav> replacement - but it could be if we add back permission checks since the attributes are largely the same. Either that or we could plan on using it going forward and just deprecate <skin:genericNav>.

We're using <skin:simpleNav> in a number of production sites, and the CPU usage has been noticeably lower.