add dual-use WriteHandle+WriteHandleKey to AnalysisBase

The next in the list of dual-use data handles that we need to get AnalysisBase functional in master.

As with previous data-handles I copied over the data handle class from StoreGate and then updated or commented out the members as needed to get the test and user code working. The plan is to leave the commented code in for now, until we have a better understanding which members are actually needed, and then remove all unneeded, commented out code at that point.