Fixed some problems + Finish implementing home screen

1. Implemented feature so that home screen can be shown by clicking home
button at the bottom.
2. Changed layout of menuinfo.xml to match with other xml files' layout.
3. Changed home button id from "home" to "home_button"
4. In AndroidManifest.xml, I added HomeActivity to the list of activity
that will be used in this application (if we try to use activity that is
not listed in the manifest, emulator spit out error and exit)
5. Modified AndroidManifest.xml file to set HomeActivity as starting
activity
6. Modified structure of code in Activities files so that it is more
readable.