support HTTP Basic Authentication

I'd like to be able to put ODM behind HTTP Basic Authentication, so that I don't have to worry about whether anyone else might try to tinker with it.  Here's a pull request that might actually accomplish this.

To use: specify a username and password in the API url, for example https://user:password@yourhost.com/path/to/odm/

This is completely untested code.  I don't even know how to build it!  I pieced it together from a couple of tutorials I found, and I'm pretty rusty at Java.  So maybe this should be considered a feature request, with some of the legwork done already, and maybe it'll even work as written :)  I hope you like it!

Keep up the good work, and thanks a ton for open sourcing ODM.