OF-1000 Prevent NPE and improve logging

Fixed group population for colliding full names.

OF-122: MUC subject change policy

MUC Invitation rejection delegate call

Improve quality of random data generation.

When a log directory cannot be created, a warning should be logged,
and null pointers should be prevented when the directory is being
referenced.

Per PR feedback, default to a strict (conforming) policy when detecting
MUC room subject change requests.

Additional work could be done to add a corresponding configuration
option to the MUC service admin console, but is not included in the
scope of this PR.

StreamIDFactory is designed to generate stream IDs. It's silly to use
something else when generating stream IDs.

Stream ID generation should be based on a strong random number generator,
should use a wider variety of characters than just hexadecimals, and
could be a bit larger for reduced chance of duplicates.

xml:lang in stream header should conform to a language tag.

toString() was called on the Locale here, resulting e.g. in "de_DE".
Instead it should be "de-DE".

Improving logging for S2S / dialback

Default to lenient policy, allowing override to strict (conforming)
policy. Tested using Pidgin, Psi, and Exodus. Refer to details in
OF-122.

Add explanation to setup about default admin password

Fix twice sending of messages on route.really-all-resources=true

The S2S (federation) code was not big on logging. This commit
introduces new logging, and structures the logged messages.
This commit does not introduce functional changes.

Add explanation to setup about default admin password
https://igniterealtime.org/issues/browse/OF-1016

When LDAP search returns a multiple result set for a user CN,
we now iterate through the entire set to find a matching user DN.

add call of sendingInvitationRejection for MUCEventDelegate

add event delegate on decline invitation

If route.really-all-resources enabled it's not requere process message again via priority algorithm.
We already processed in 560 line. 
If we not stop (return) than session.process() call twice (first in line 560 and next in next other)

ofmeet plugin removal
Looks like I have to approve this myself. Here goes

Move openfire meetings from core repository

OF-1011: Trim each line of a PEM representation

Admin console: SSLv2Hello isn't a protocol, but an option.

OF-1006: Improve handling for pooled resources

OF-856: Cherry Picking of linuschien solution

Optimized configuration for XMPPPacketReader pool; improved exception
handling and reporting.

OF-1009: Ignore the exception indicating an error

This commit is a cosmetic change to the admin panel. If the JVM supports
SSLv2Hello, it is no longer presented as an encryption protocol, but rather
as an option.

Although not 'properly ended', the handshake failed in an expected manner.
This should be processed as a 'normal' handshake failure (not an exceptional
one).

OF-1010: Cannot re-init default SSLContext

OF-1008: Prevent loops of message failure

OF-793: Improve exception message

When the local user that is sent a message delivery failure report is
not online, drop the stanza. This prevents loops where the failure
to deliver the failure message triggers another failure message.

This commit makes handling of stanzas that could not be delivered uniform,
in regards to logging. Other than log levels and messages, this commit does
not make a functional change.

A default SSLContext object cannot be re-initialized. This causes LDAPS to fail.