Improve handling of "button pressed" event

[astrabykin]

Another improvement we should do is to ignore button pushes in certain states, to avoid that they can queue up. For example, if the player now pushes the button while the image is being analysed, it is being queued so that another image recognition starts immediately when the current one is finished.

[akoptelov]

By default if an event on the top of the queue is not accepted by any capsule is just dropped.

It looks like recognition result and push button events are put in the queue in the wrong order. Possibly this is because of how the HttpServer component is implemented. See rtapp_20190909_181616883000.zip.

It looks like raising the priority of push button event fixes the problem as it is handled in the state before any other event and discarded if not applicable.

@astrabykin please confirm.