JBIDE-15640 BrowserSim: use JavaFX WebView as a browser engine

- removed all references to org.eclipse.swt.browser.Browser
(this will allow to use JavaFX browser when
we will create IBrowser implementation using JavaFX):
  - added org.jboss.tools.vpe.browsersim.browser.IBrowser interface
  - created SWT Browser listeners adapters (org.jboss.tools.vpe.browsersim.browser.ExtendedCloseWindowListener and similar)
  - changed all references in BrowserSim/CordovaSim from org.eclipse.swt.browser.* to org.jboss.tools.vpe.browsersim.browser.*