adaptable TWindow width

Just like there's a need for adaptable Topology.poll() behavior (QUARKS-131), applications will need the ability to adapt a window's width as demanded by conditions.

e.g., maybe a condition occurs that motivates increasing the window width to improve the accuracy of an analytic. Or maybe the app decides that it should reduce the width as a result of processing time or memory pressure concerns.

Notes:

• add TWindow.alias(), getAlias()
• time based window would register and handle PeriodicMXBean
• count based window would register and handle a new MBean - e.g., CountMXBean ?