Merge pull request #894 from jbertram/master

Doc updates
I added a new test to check null values.
Merge pull request #895 from diegolovison/master

I added a new test to check null value.
Fix typo in method name.
Rename method to an accurate name ('close' is misleading)
HORNETQ-1128 Improve schema documentation, add some intra-manual links
Add description to assertion in test.
HORNETQ-1148 Bump the version to fail properly if server is older:
Connecting from a 2.3-client (now, version 123) to a 2.2 server will fail due
to serialization errors. Better a `version incompatibility` error.
First close all sessions, THEN start waiting for completion.
Remove the setContext call, from server.stop() as the methods inside
ServerSession are already handling the context switching.

Also make the sessionContext 'final', it simplifies the code and we
can assume more about it
Merge pull request #898 from FranciscoBorges/stop-server-sessions

First close all sessions, THEN start waiting for completion.
Merge pull request #897 from FranciscoBorges/version-hq-1148

HORNETQ-1148 Bump the version to fail properly if server is older:
Merge pull request #896 from FranciscoBorges/schema

HORNETQ-1128 Improve schema documentation, add some intra-manual links
Make synchronization of "started" field consistent.
Merge pull request #899 from FranciscoBorges/smallFixes

Make synchronization of "started" field consistent.
We should disable page cleanup during sync otherwise a page may survive what would make it deliver extra messages after a failover
This task was done with Howard Gao's help where he found a test where we could replicate this issue
HornetQ-1114 listMessagesAsJSON and countMessages JMX methods do not include paged messages

Added a totalIterator() to iterate a queue's messages including those in the paging store.
Merge pull request #900 from clebertsuconic/master

Disable page cleanup during sync as that could lead to data lost or duplication
Rename compactorEnabled --> compactorRunning
HORNETQ-720 Must call pageManager.resumeCleanup() also in case replication is aborted
Merge pull request #901 from gaohoward/howard_hq1114

HornetQ-1114 listMessagesAsJSON and countMessages JMX methods do not inc...