Massive cleanup of the Munin ports:

• Use a fixed UID / GID
• Fix handling of sample configs in plists
• Add missing plist entries (mostly directories)
• Use /var/munin instead of %D/var/munin
• Consistently use %%FOODIR%% instead of ${PREFIX}/foo etc.
• Honor BATCH / PACKAGE_BUILDING
• Fix network throughput probes (if_ and if_errcoll_)

PR: 120755, 120756, 124528, 129576, 129577, 143804
Submitted by: see PRs
Feature safe: yes