Improvements for new security approach

1. The visor tasks lost permission.
The method VisorQueryUtils#scheduleQueryStart makes a new thread and loses context.
2. The GridRestProcessor does tasks outside "withContext" section. As result context loses.

In additional: 

Change a java docs for TaskEvent, CacheEvent, CacheQueryExecutedEvent and
CacheQueryReadEvent.
"Gets security subject ID initiated this task event, if available.
This property is not available for GridEventType#EVT_TASK_SESSION_ATTR_SET
task event.
Subject ID will be set either to node ID or client ID initiated task
execution."

by:
"Gets security subject ID initiated this task event if IgniteSecurity is
enabled, otherwise returns null."