change Metric element of a Canvas::Ruler item into a pointer internally
add Canvas::Ruler::set_metric() to allow ruler metrics to be changed dynamically
rename system and user config files with product-neutral names
fix packaging scripts to use new system config file name; NOTE: this file should probably be included in Windows packages but appears not to be

Conflicts:

	tools/linux_packaging/build
change all GUI config files (GTK RC and our own XML config files) to use product-neutral names

Conflicts:

	gtk2_ardour/ui_config.cc
	gtk2_ardour/ui_default.conf.in
	gtk2_ardour/wscript
Ensure complete sync with previous UI configuration files
(since some changes here were cherry-picked from the waves codebase)