Avoid Exceptions from existing models with no metamodel uris

* Appears that WSDL created models lack primary metamodel uris and the
  method getModelClass() returns null causing exceptions.

* Returns something tangible rather than null
Fix incorrect use of window listener in plugin start

* Incorrect to use PlatformUI.getWorkbench() in a plugin's start method
  since the workbench may not have been initialised yet.

* Correct solution is to use an IStartup implementation which is fired
  once the workbench has been displayed.
Merge pull request #95 from phantomjinx/master

Udf works seems to have popped up a source of NPEs
Improve usability of Default Server Action

* ModelerCore
 * Only close editors if the server version actually changes, as different
   servers but the same version will not require a different runtime client

* SetDefaultServerAction
 * Added to the Guides view so taiored accordingly
 * If their is a change in server version and there are open editors then
   ask the user if they wish to continue since the editors will be closed

* ServerSelectionDialog
 * Cosmetic improvements to layout
 * Better map for storing keys to servers

* RuntimeAssistant
 * Used for executing the default server action in the same manner as the
   edit server action
 * selectServer method for displaying the ServerSelectionDialog, logic taken
   from the EditServerAction and generalised.
Merge pull request #97 from phantomjinx/master

Improve usability of set default action
TEIIDDES-1523 further refinement of object editor panels.
Inserted procedure type selection dialog prior to opening New Procedure dialog.
Added checks to prevent creating objects with invalid names
TEIIDDES-1586 removed schema and catalog as supported objects
Fixed parsing issue that prevented importeding tables with no description
Add a small default server status panel to Model Explorer view

* Provides a small collapsible panel that shows the current default teiid
  server and version

* ModelerCore
 * Need to allow server manager to set the default server to null if all
   servers are deleted
 * Notify listeners of server change even if there is not a server version
   change

* ITeiidServerVersionListener
 * Addition of method for serverChanged so listeners can be notified of
   a change of server even without a change of server version

* ModelExporerResourceNavigator
 * Adds form section to bottom of view, showing current default server and
   its version.
 * Hyperlinks to servers view from value of server
 * Updates on server and server version changes
Merge pull request #98 from phantomjinx/master

Panel for default server
TEIIDDES-1010 fixed issues creating/naming indexes
includes fixing the Name In Source value