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.
Automation Controls (and controls in general) are now
only updated in realtime context. Either via automation-playback,
or via SessioEvent. This directly sets the Control:_user_value
(before emitting the Changed signal).
The GUI does not need to evaluate the control at a given point
in time, so the API call can be removed and unified.
This commit first removes all calls to "get_double" to ensure
that no special cases exist.
