(JBIDE-13400) PageContextFactory.ExtendedLinkElementAdapter is leaked
The issue is fixed by avoiding the adding of ExtendedLinkElementAdapter to the nodes.
ExtendedLinkElementAdapter is used only on a temporary basis and as such no leaks should occur.

	modified:   plugins/org.jboss.tools.jst.css/src/org/jboss/tools/jst/css/dialog/selector/model/CSSJSPRecognizer.java
	modified:   plugins/org.jboss.tools.jst.css/src/org/jboss/tools/jst/css/dialog/selector/model/CSSSelectorTreeModel.java
	modified:   plugins/org.jboss.tools.jst.text.ext/src/org/jboss/tools/jst/text/ext/hyperlink/CSSClassHyperlink.java
	modified:   plugins/org.jboss.tools.jst.web.kb/src/org/jboss/tools/jst/web/kb/PageContextFactory.java
	modified:   plugins/org.jboss.tools.jst.web.kb/src/org/jboss/tools/jst/web/kb/internal/proposal/CSSClassProposalType.java
JBIDE-13488 Test for New Checkbox wizard

Created generic test for testing palette tools and specific case
for check box entry.
For test mode, provided execution of drop command in JSP text editor
in the main thread.