Add additional help text to the REPL and some other REPL improvements

[daveaglick]

A better introduction and help text should be available for the REPL. For example, it's not clear what Help() does or that you can pass it an object to get a list of methods on the object.

For that matter, it would be helpful if the Help() method also printed the type. Dump() (see #208) could work the same way too.

I.e. Help() prints the type information like properties, methods, etc. while Dump() prints a values of those properties.