Avoid deadlock by using the same object to synchronise open calls

* Possible to have the UI thread taking ownership of the
  ModelWorkspaceManager with another thread owning the openLock. Thus, the
  2 threads can become deadlocked.
TEIIDDES-1457: Add a reference to the SYSADMIN external resource

* The SYSADMIN model in the System.vdb is never added to the set of
  external resources hence its functions are not available to the SQL
  parser and resolver.
Adds visualisation to execution plan view

* .project
 * External builder for zipping up the execution plan website data payload
   as its more efficient for java to unzip it into the temporary directory
   rather than copy each invidual file.

* Removes the old PlanToHTML.xsl which appears redundant

* Adds Visualisation tab to execution plan view, displaying a browser
  widget containing an html of the plan. Creates an execution-plan temp
  directory and unzips its javascripts, css and images files. Should only
  happen the first time an execution plan is requested.
Merge pull request #237 from phantomjinx/8.2.x

Tidy up, #1457, visualisation for execution plan view