Bootstrap class loader support

Run glowroot in the bootstrap class loader. This is needed for Wildfly
since jboss module class loaders cannot see the system classloader, but
can see the bootstrap class loader.

Also, add support for weaving classes that are in the bootstrap class
loader, e.g. java.net.Socket.
Use guava StandardSystemProperty where possible
TEMP SAUCE LABS ON TRASK/GLOWROOT