[2.3.x] + fix javadocs according to the issue #1583
https://java.net/jira/browse/GRIZZLY-1583

createSimpleHttpServer does not document it accepts null
[2.3.x] + fix issue #1584
https://java.net/jira/browse/GRIZZLY-1584
"Error page sometimes is sent with content-length == 0"

+ implement feature #1585
https://java.net/jira/browse/GRIZZLY-1585
"Introduce error page generation API"
[2.3.x] + fix the issue #1586
https://java.net/jira/browse/GRIZZLY-1586

"SyncThreadPool may stuck due to a racing issue"
[2.3.x] + fix the issue #1587
https://java.net/jira/browse/GRIZZLY-1587

"ConnectionPool's keep-alive/reconnect management thread is not getting stopped"
[2.3.x] + optimize HttpClientFilter by removing responseQueue.contains(message) check
[2.3.x] [maven-release-plugin] prepare release 2_3_6
[2.3.x] [maven-release-plugin] prepare for next development iteration
[2.3.x] + fix the issue #1588
https://java.net/jira/browse/GRIZZLY-1588

"Request.getHttpHandlerPath(), which corresponds to a servletPath, could be null"