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.
I agree that it's mildly cumbersome to repeat this so much. I was wondering if it might be desirable to refactor Game.js a bit so that it doesn't *need* to call ```arrangePage()``` in so many places: if most of these methods are being called by ```Game.showStatePage()```, would it be reasonable to just have it called at the end of *that*? Or is there a reason that would be a bad idea?