Add support for Java 8

[samuelcampos]

Update jetty-runner to support java 8.

When accessing the http://localhost:8080 while running axiom using java 8, the following exception was being thrown.

ERROR: Compilation error
org.eclipse.jdt.internal.compiler.classfmt.ClassFormatException
	at org.eclipse.jdt.internal.compiler.classfmt.ClassFileReader.<init>(ClassFileReader.java:372)
	at org.apache.jasper.compiler.JDTJavaCompiler$1.findType(JDTJavaCompiler.java:367)
	at org.apache.jasper.compiler.JDTJavaCompiler$1.findType(JDTJavaCompiler.java:324)
	at org.eclipse.jdt.internal.compiler.lookup.LookupEnvironment.askForType(LookupEnvironment.java:102)
	at org.eclipse.jdt.internal.compiler.lookup.UnresolvedReferenceBinding.resolve(UnresolvedReferenceBinding.java:49)
	at org.eclipse.jdt.internal.compiler.lookup.BinaryTypeBinding.resolveType(BinaryTypeBinding.java:122)
	at org.eclipse.jdt.internal.compiler.lookup.PackageBinding.getTypeOrPackage(PackageBinding.java:168)

...