improve $RepeatedMsgReduction doc

Thanks to David Lang for some of the text.
some more clarification on repeat message reduction
fix import errors
fix import problems
Merge branch 'v5-stable' into v7-stable

Conflicts:
	source/installation/install_from_source.rst
	source/messageparser.rst
move non-global config statements out of global tree
Merge branch 'v5-stable' into v7-stable

Conflicts:
	source/configuration/index.rst
Merge branch 'v7-stable' into v8-stable