ConfigKey BrooklynNode.CLASSPATH to List<String>

Was String; now relies on TypeCoercion's conversion from comma-separated String to List<String> to support List<String> natively in code while still allowing an entry in brooklyn.properties to work. Note that this changes the brooklyn.properties format from ;-separated to ,-separated classpath entries. Also removes the @Beta annotation from the CLASSPATH configkey
BrooklynNodeIntegrationTest: test classpath config