Switch to html5mode for pretty URLs

Switch from hashbang URLs to prettier URLs using html5mode, e.g. `/hawtio/index.html#/jvm/connect` becomes `/hawtio/jvm/connect`.

Note the switch from `index.html` to `index.jsp` to ensure base href is set to match context that the app is served under in case someone changes it from the default `/hawtio`. Using `index.jsp` as default 404 page allows this to be served if no resource is actually foumd & then AngularJS can do it's stuff, routing appropriately.

This works fine with everything I've tested, except proxy requests don't have a nice URL. They effectively look like they're local, even when they are actually proxying. Discussed in #1380 & this can be fixed later, once a better URL scheme is defined for remote connections.