Start to accomodate optional columns.
Use {} to zero-initialize structs rather than {0}.
sCompare support.
Whitespace.
Whitespace.
Remove SourceServer and Source_Client for now.
Use ConcreteHead rather than separte required/optional RelHeads.
Return indication that work was done when joining.
Safer invocation of enqueued callables.
Emit better text for ConcreteHead.
Use 100e-3 rather than 0.1 as the representation of 100ms.
Source clarification.