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!!