total reimplementation of Configuration object internals to make adding new config...

total reimplementation of Configuration object internals to make adding new config vars an order of magnitude simpler. the actual path taken is a bit of a kludge, to put it mildly, but adding a new variable is now basically just one line in configuration_vars.h, and no work is required for serialization to/from ardour.rc.

git-svn-id: svn://localhost/trunk/ardour2@420 d708f5d6-7413-0410-9779-e7cbd77b26cf