Moved many things to Login.js

Resolves #1112.

http://jenkins.buttonweavers.com:8080/job/buttonmen-AdmiralJota/399/

In addition to the tests for whether or not the player is logged in, I also moved a bunch of common code from the ```Foo.showFooPage()``` and ```Foo.arrangePage()``` methods in the individual files to ```Login.arrangeHeader()``` and ```Login.arrangePage()``` so that it can be shared. 

Most pages don't even need their own ```arrangePage()``` method anymore (so I took them out, just having them call ```Login.arrangePage()``` instead), and there are several pages where we should probably merge ```Foo.showFooPage()``` with ```Foo.getFoo()``` at some point, since there's so little there now.
Yup, that sounds good. And we could do essentially this same thing via my suggestion on the previous line note, without needing to add extra logic to the HTML file, if you'd like.