Adds websocket capabilities compliant with the latest specifications
(RFC 7395).

Note that the new component is implemented as a plugin, but I have
included a few small modifications to core classes to improve
extensibility.

I have tested these changes using the stanza.io client library on both
Chrome and Firefox.

FIX: Monitoring plugin list request with max tag does not work correctly

OF-631: Implement SCRAM support

Initial xep-0198 message ack implementation

OF-903: Simplify backup packet delivery

Original issue (OF-857) has been addressed by providing an alternate
packet deliverer (to offline storage). This additional logic was an
ill-advised "belt-and-suspenders" attempt to prevent the recursion which
was occurring before the backup deliverer was implemented.

After discussion with Jonny, switched the existing Map to a Deque, and in
response to Tom's suggestion, added XEP-0203 (and legacy) delay stamping.

Tested using Gajim and Swift; testing the delay stamping was done by disabling
the acknowledgement handling to force retransmission.

This patch adds a basic, non-resumable, XEP-0198 acking solution. It will
redirect "lost" messages to offline storage, but does not attempt to suspend
the session, so will not allow any resumptions.

This implements the SCRAM-SHA1 mechanism, and includes extending the existing
DefaultAuthProvider to store the Scram hashes for faster authentication.

If user.scramHashedOnly is set to true, then only these non-reversable hashes
are stored (and thus security is increased in exchanged for removing support
for DIGEST-MD5 et al).

Add Proxy Authorization to DefaultAuthorizationPolicy

Fix some javadoc warnings found with `ant javadoc` build target

fix XML Schema instance namespace in two XML Schema files.

Improve installation guide

FIXED:  typo

FIXED:  typo

Fix collection requests XEP-0059

XEP-0202 Entity Time should respect Daylight Saving Time

Fixes OF-932

FIXED:  typo

1. 'from' was 'fro' (Line 18)

https://igniterealtime.org/issues/browse/OF-931

OF-682 Add Portuguese as option for server-locale

Restored and separated Database-Query for MYSQL

Update spanish translation

This patch repairs an incompatibility of the current default PURGE_FOR_SIZE - SQL-query by adding a separated variant for the database-type mySQL.
Previously this incompatibility was provoked by "fixing" the default-query for hsqldb - see OF 789 [https://igniterealtime.org/issues/browse/OF-789] and thread on https://community.igniterealtime.org/message/250575 )

OF-929
https://igniterealtime.org/issues/browse/OF-929

OF-929-Add the ability to generate messages in the userCreation plugin (for monitoring plugin tests)

There is a deadlock while reading the state variable if close() is running.

This switches the state to be volatile instead - it's only written to inside
the lengthy close() lock, so this should be reasonable.

OF-889: Added try-catch blocks to the various JSP pages where Session.getHostName or Session.getHostAddress is called to prevent the Sessions tab from showing UnknownHostExceptions when there are bad client sessions laying around

FIX: Monitoring plugin list request with max tag does not work correctly
https://community.igniterealtime.org/thread/56168

For more information:
https://community.igniterealtime.org/thread/56173

Monitoring Plugin request of collection count according 2.7 of XEP-0059
More information on https://community.igniterealtime.org/message/250310