Add 'controls' item to plugin insert context menu to always show Ardour generated controls for plugin, even if the plugin has a GUI. In particular, this gives you UI access to presets and the other handy stuff ardour sticks at the top, for inherently broken external UIs which don't allow Ardour to add such things.
Fix crash related to scale points when showing plugin UIs.
Fix packing of scrolled generic plugin UI so the controls expand (rather than leaving a ton of wasted empty space and using unnecessary scroll bars).
git-svn-id: http://subversion.ardour.org/svn/ardour2/ardour2/branches/3.0@9551 d708f5d6-7413-0410-9779-e7cbd77b26cf