FELIX-1988 Apply 5.main_template.patch by Valentin Valchev (thanks) with the following changes: (1) also externalize the footer as a template (for consistency), (2) create a readTemplateFile method to read the file, (3) return an empty string (instead of using null) of the file fails to be read
felix/trunk/webconsole/src/main/java/org/apache/felix/webconsole/AbstractWebConsolePlugin.java
felix/trunk/webconsole/src/main/resources/templates/