LoginActivity on non-xhdpi screens

Hi,

while playing around with with my old Samsung i9000 I noticed that LoginActivity overlapped the button and the help text, because there is not enough space on the screen while the keyboard is displayed.

![Screenshot1](http://i.imgur.com/u5Obem.jpeg)

I modified register.xml, removed the `RelativeLayout` and merged all elements into the previously nested `LinearLayout`. I also modified the Views to match the new layout.

It should look more or less the same on larger screens, but should now correctly scroll on smaller screens. I guess that was your original intention, since everything was wrapped in a `ScrollView`.

Please check it out, you might want to modify the details to your likings.

![Screenshot2](http://i.imgur.com/E4Fqkm.jpeg)


P.S.: Keep up the great work!