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 think you'll find what you're looking for around lines 96-114 of Login.js. The bit that your annotation is on is just telling it not to try to display the div if it wasn't able to create the div earlier.