Cleaning up/genericification of Insert interface.
Fixed meter count for pre-fader metering (was # inputs, not # channels at end of pre-fader redirect list).
Work on redirect list stream handling, better error reporting (towards automatically adding 'adaptors' in the future?).
git-svn-id: svn://localhost/ardour2/trunk@2025 d708f5d6-7413-0410-9779-e7cbd77b26cf