Vectorized the buttons, adjusted login page, etc...

I have made the following changes:

Removed the button images and their respective XML file.
Added images of Submit, Register, and Use as Guest.
Added a shape XML that makes a rounded gradiented rectangle for buttons with press states.
Changed activity_login.xml to accompany these new buttons (in a RelativeLayout that overlays the text images over the XML shape). The buttons now fill the screen horizontally on any sized screen, and are now wider in landscape mode. The ram logo has been shrunk a bit to accompany the buttons.
Edited fragment_map.xml to move the radio into 2 lines, as it was too wide for many devices.
Made a background for the login activity when in landscape mode, as the original background is too stretched in landscape. layout-land/activity_login.xml has been modified to use the new background.