* Run python self tests with a messageDelay of 100ms. Message delay is used
  in function "delayDisplay" to (1) let the event loop catch up to the state
  of the test and (2) to display a meaningful message when running test
  interactively from Slicer.

  When running tests on the dashboard, there is no need to wait too long
  before each test steps. This commit sets a default of 50ms when tests
  are executed from the module panel. It also provides a Slicer to change
  the value.

* Refactor tests to use ScriptedLoadableModule base classes

* Remove redundant test case AbdominalAtlasTest already coverted by
  AtlasTests

* Remove duplicated implementation of functions like takeScreenshot.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@27617 3bd1e089-480b-0410-8dfb-8563597acbee