Javadocs cleanup.
Removed rotten comment and cleaned up javadocs.
Made test more robust.
Calling notIdle() to avoid the idle timeout triggers when sending frames.
Cosmetics: removed unused imports, cleaned up source code, improved javadocs.
445167 - Allow configuration of dispatch after select.

Introduced parameter "dispatchIO" in the relevant factories so that
they can be configured by users and connections will be created
taking into account this parameter.

For less configurable connection factories, this parameter is
currently hardcoded to either true or false depending on the case.
For example, ALPN and NPN connections have it to false, since they
don't do any blocking operation in onFillable().
Fixed race where the key interests were set before updating the
state, causing onSelected() to be called with the wrong state and
failing an assertion.