JBIDE-8428 Content assist inside #{} in text element of xhtml shows JSF tags as proposals

The issue is fixed. All the Non-EL proposals are filtered out from the proposal list when the Content Assist
is invoked from the position inside EL (#{...}).
JUnit Test org.jboss.tools.jsf.jsp.ca.test.CAELNoTagProposalsInELTest

	modified:   plugins/org.jboss.tools.jst.jsp/plugin.xml
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/HTMLTextViewerConfiguration.java
	deleted:    plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/ITextViewerConfiguration.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/JSPTextViewerConfiguration.java
	deleted:    plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/TextViewerConfigurationDelegate.java
	new file:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/contentassist/ELPrefixUtils.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/contentassist/JSPDialogContentProposalProvider.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/contentassist/computers/AbstractXmlCompletionProposalComputer.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/contentassist/computers/FaceletsELCompletionProposalComputer.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/contentassist/computers/FaceletsTagCompletionProposalComputer.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/contentassist/computers/JspTagCompletionProposalComputer.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/contentassist/computers/XmlELCompletionProposalComputer.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/contentassist/computers/XmlTagCompletionProposalComputer.java
	modified:   plugins/org.jboss.tools.jst.jsp/src/org/jboss/tools/jst/jsp/jspeditor/info/FaceletTagInfoHoverProcessor.java