Object Versioning: fixed lively.ObjectVersioning.isProxy

a non-proxy object might have a proxy as prototype, but this check
still should return false for this object being a proxy
Object Versioning: a couple of pending __proto__ test cases

essentially, using a proxy as prototype seems to work (see other
test cases), but reading and writing the __proto__ slot doesn't
seem to work correctly
Object Versioning: source transformations, proxies for literals

literals for objects, arrays, and functions should be automatically
wrapped in functions that return Object Versioning proxies for these
new objects
Object Versioning: tests whether arrays are handled like objects