OF-947: Overlay should be able to modify i18n

i18n files can now be modified by files in <overlay>/i18n/. Files are merged,
where the overlay values have preference over the original values.

This commit removes support for the (poorly implemented) overlay.properties file.

Openfire now requires Java 7, not Java 5.

Problems are inevatible when a resource is opened, passed around
and closed by a different method. This can improved upon easily.

Updated the REST API plugin to 1.1.6

Fixed: the problem with wrong media type by error

Minor improvements to spelling

OF-943: Fix timeout issues in HZ plugin

This updates the plugin metatdata to prepare a release for the timeout
bug fix which was previously committed (via PR#288).

OF-943: Timeout issues on synchronous cluster tasks

Details: https://community.igniterealtime.org/message/252259#252259

Update the REST API plugin to 1.1.5

- Added: Send broadcast message to all online users

Note: this is the 'v4', which is Java1.6 compat

OF-939: Should have safeguards against runtime exceptions.

ofmeet plugin ver 0.2.0

Updated plugin date

Updated Jitsi Videobridge to latest code
Removed support for jingle nodes, redundant.
Used IP Address instead of host name for NAT_HARVESTER_LOCAL_ADDRESS and NAT_HARVESTER_PUBLIC_ADDRESS.

https://community.igniterealtime.org/message/251558

Update the REST API plugin to 1.1.4

- Added: get concurrent sessions (local or cluster wide)

Get count of unread messages in REST API plugin & added new callback plugin which call a url if user is offline

OF-938: Use correct namespace for BOSH packets

Fixed Kerberos SSO Challenge Response

2) Implemented change as per Kalchenko Alexandr (https://community.igniterealtime.org/thread/55544)

fixed MySQL Error 1093 in monitoring plugin ConversationManager & added description

Update default HZ config file to match new schema

Per community feedback here:
https://community.igniterealtime.org/thread/56508

2) fix MySQL Error 1093(can't modify the same table which is used in the SELECT part) in ConversationManager

Hazelcast 3.5.1 update