v3 roadmap

[garronej]

• Get rid of the need to add the $ when attaching with operator.
• Support for async operators ( other than with "evt/asyncPipe").
• Create SelfManaged operators for more complex operation.
• StatefulEvt: Get rid of evtDiff, evtChange, evtChangeDiff the onlyWhenChanged operator is preferable.
• Way (via an operator) to get from an evt a new instance that only postAsyncOnceHandled.
• We should be able to create StatefullEvt where the initial state is only computer when accessed Evt.create(()=> "initial state" )
• ctx.evtDoneOrAborted() should be a StatefulEvt