Passing command groups as lvalue-references to other command groups should be illegal, as their copy constructors have been deleted. However, copy constructors are const-qualified. This led to a very obscure bug where passing a command group by lvalue to another command group would result in a valid template expansion 'looking like' a copy constructor, and being preferred to the deleted copy constructor. This would result in constructor recursion (the expanded constructor would, in an attempt to call the copy constructor, call itself), and an eventual segfault when the stack inevitably overflowed.
This fixes the problem by explicitly deleting the problematic constructor signature - attempting to do this now (correctly) generates a compilation error.
This removes the name and subsystem from individual objects, and instead
puts this data into a new singleton class, SendableRegistry. Much of
LiveWindow has been refactored into SendableRegistry.
In C++, a new CRTP helper class, SendableHelper, has been added to provide
move and destruction functionality.
Shims for GetName, SetName, GetSubsystem, and SetSubsystem have been added
to Command and Subsystem (both old and new), and also to SendableHelper to
prevent code breakage.
This deprecates SendableBase in preparation for future removal.
This is the C++ version of #1682.
The old command framework is still available, but will be deprecated.
Due to name conflicts, the new framework is in the frc2 namespace.
Eventually (after the old command framework is removed in a future year)
it will be moved into the main frc namespace.
