[wsrp-wsia] Issue #24 Adding previousWindowState to getMarkup operation

[Rich Thompson <richt2@us.ibm.com>]

The proposal here is to eliminate the draft v0.7 semantics of the Consumer
keeping a stack (maybe size=1) of previous modes and windowstates per
entity per user (memory intensive) in favor of the entity remembering the
mode/window state transitions it cares about and requesting the right one
on the way back. The only example to date for this is the exit from help
going back to either view or edit depending on what the End-User had been
doing. It has also been noted that Consumers who wish to provide such a
stack as a service may define these as custom modes/window states.

I would agree with removing the previous_mode and view_previous
constants/semantics.