Fix banner scaling in game list.

-In GameListAdapter.java, the existing scaling code is unnecessary and stops Android's built in scaling from doing its job.
-In gamelist...etc.xml, set the icon's width to 100 density-independent pixels (i.e. have android figure out how to make it the right size.)
Merge pull request #524 from sigmabeta/android-banner-scaling

Fix banner scaling using a different method.