Simply repeated dwd's commit 73b59106 on Ubuntu Trusty (20170717~14.04.1)

* OF-1356 add section for Windows x86 to x64

* OF-1356 formatting fixes

* add missing </li>

getIterations() threw an exception which
caused early termination of the SASL exchange.

Spotted by Phil Roberts of Surevine Ltd.

This implementation is a backport from master to the 4.1 branch, of an API change that was part of OF-1353. OF-1020 needs this API. This specific implementation should not live outside of the 4.1 branch.

There's no point in offering in-band registration when the user provider disallows any modifications.

Fixing NullPointerException caused by having a mix of valid Groups and NULLs inside the result of getGroupsFromKeys

Openfire 4.2.0 will have the functionality that's now in the websocket plugin. As a result,
this plugin should not be used in Openfire 4.2.0. To facilitate this, we've defined a new concept
of 'priorToServerVersion' in OF-1353.

This commit defines that the plugin should only be used in Openfire instances prior to version 4.2.0.

This PR implements the missing code and fixes the issue

   @Override
   public ConnectionConfiguration getConfiguration()
   {
       // TODO Here we run into an issue with the ConnectionConfiguration introduced in Openfire 4:
       //      it is not extensible in the sense that unforeseen connection types can be added.
       //      For now, null is returned, as this object is likely to be unused (its lifecycle is
       //      not managed by a ConnectionListener instance).
       return null;
   }

This is a complex problem.  During setup, fetching xmppSettings from the session may fail due to an invalid session state maintained between the client browser and the server.  This is likely caused by a previous HTTPS session to the same server hostname setting a `JSESSIONID` that subsequently can not be overwritten by the current HTTP openfire-setup session.

This introduces i18n string `setup.invalid_session`

Usage of Mapped providers requires a lot of configuration, that should be documented. The documentation provided in this commit describes a common use case, in which admins are to be retrieved from the default providers, while regular users are obtained from an external system.

XMPP defines two configuration fields for password-protecting a room:
- one that defines if the room is password protected.
- another one that defines the password.

Openfire, internally, only stores the password, if password-protection is required.

Some clients send only a password, without explicitly defining the password-protection boolean. In such cases, Openfire should be somewhat flexible, and process the configuration form as intended by the user.

* OF-1343 added comments about changes in 4.1.5

* OF-1343 a note about new service behavior

The static web content handler is allowed to be null (when there's no static content to be served). In such case, the null-handler shouldn't be loaded in Jetty (which will throws nullpointers).

* OF-1342 Remove "Run Openfire" from the final step of the installer. Changed to "Start Openfire Service"

* OF-1342 Remove "Run Openfire" from the final step of the installer. Changed to "Start Openfire Service"

* OF-1349 Create separate Windows installer with and without JRE

This commit fixes a runtime problem caused by SortedSet usage with providers that are not Comparable. By using a different Set implementation, iteration order is predictable, without there being a need for providers being Comparable.

This commit adds some UX improvements to the 'edit group' page on the admin console.