Merge pull request #266 from phantomjinx/master

TEIIDDES-1935: Tidy up paths through setting the default server
TEIIDDES-1941: Stop unreleased server versions being targeted by default

* The value of the 'default server version' is derived from the servers
  configured then a set preference and finally an algorithm based on
  runtime plugins installed.

* The latter algorithm simply found the highest version that the installed
  runtimes were compatible with and displayed returned accordingly. However,
  the introduction of adding in unreleased teiid versions has meant the
  display of versions like 8.9.x which looks silly to the user.

* Algorithm modified to only display the highest version compatible if
  less than or equal to the last tested version, ie. 8.4.x. The user is
  free to set it higher if they wish but at that point they should know
  what they are doing!!
TEIIDDES-1475: Workaround for the title causing Group layout problems

* Instead of using group.setText, this adds the title as a single lable at
  the top of the group.

* Since some clients use the WidgetFactory.createGroup method then proceeed
  to modify the layout of the group themselves, the span of the layout may
  be incorret, resulting in the title being added to the same line as other
  child components. To avoid, a paint listener is added to the group that
  sets the grid data properties of the title at the last possible minute.
  This ensures the title remains on a line on its own.
Avoids an NPE if the preview manager's server is null
WIP