move important stuff to top of toc
Merge branch 'v5-stable' into v5-stable-restructure
remove outdated "bugs" listing

This has long been superseeded by the bug trackers
see also: https://github.com/rsyslog/rsyslog-doc/issues/42
remove outdated rsyslog/syslog-ng comparison

see also: https://github.com/rsyslog/rsyslog-doc/issues/42
Corrected merge conflicts.
Merge branch 'v5-stable' into v7-stable