Fixes errors for missing file URLs for spring configuration locations

[jgibson]

This fixes issue #39. I had to tweak the build a bit to get it to accept a different name on the copyright header, if there's a better approach to that then let me know.

[jgibson]

These tests are just ensuring that the WebLogbackConfigurer doesn't throw an exception when provided with missing URLs and instead falls back to the default logging configuration.

I guess that we can stick an assertTrue() at the end of these to show that the test was successful. A stronger test would be to ensure that the default logging initialization occurred, but I don't know how to do that. Even if we could do the test it would be fragile if a developer specified their own logging configuration via a system property or a configuration file.

[jgibson]

OK, after a little thought and poking at Spring's MockServletContext I realized that it wasn't too difficult to test out the error messages for missing configurations. A user who has specified their own logging configuration may still break the test, but it's less likely now.

[tony19]

I tried rebasing this onto master, but it did not compile (symbol not found, bad @Override, etc.). Can you please rebase? See wip/pr40.

[jgibson]

I'd totally forgotten about this one. Anyways, sure, I'll take a look by next week.