Modified xml files and logo designs

activity_startup.xml was renamed to startup_activity.xml to reflect the
name of the corresponding activity, and its format was simplified to
consist of a single TableLayout enclosed in a ScrollView. Layout_height
and Layout_width were also changed for certain elements to correctly
resize to the device screen.

Both the logos on the About page and the SplashScreen were also
recreated to reflect "UAH Rowing" instead of "UAH Crew".