Previously directly using Luawindow::instance() was able
to create the window, bypassing the Window Manager, this resulted
in two issues, the first being rather significant:
* `LuaWindow::set_session()` was not called
* The Window was not maked as visible in the Window menu
This is mostly a simple lexical search+replace but the absence of operator< for
std::weak_ptr<T> leads to some complications, particularly with Evoral::Sequence
and ExportPortChannel.
* remember window visibility, size and position
* Show as toggle in the window-menu (rather than show action)
* reduce specialization, use WM and ArdourWindow infrastructure
(transient parent, window-type, etc)
Copyright-holder and year information is extracted from git log.
git history begins in 2005. So (C) from 1998..2005 is lost. Also some
(C) assignment of commits where the committer didn't use --author.
