the rest from `tools/convert_boost.sh`.
* replace boost::function, boost::bind with std::function and std::bind.
This required some manual fixes, notably std::placeholders,
some static_casts<>, and boost::function::clear -> = {}.
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.
This also removes Route::group_gain_control() and associated machinery.
Not yet tested with Mackie or other surfaces. More work to done to
start using the group capabilities, and also potentially to add
or derive more controls as RouteAutomationControls
