Fix the Mobile networks icon in Settings

-shrinked a little
-centered

See the screenshots:  https://drive.google.com/folderview?id=0BxY75MbFAKsXMzF3YXJZdUhVNm8&usp=sharing

Change-Id: Ia77dbf4417a3c4dd09adc11990406e97b482ae46

Conflicts:
	res/drawable-hdpi/ic_settings_mobilenetworks.png
	res/drawable-mdpi/ic_settings_mobilenetworks.png
	res/drawable-xhdpi/ic_settings_mobilenetworks.png
	res/drawable-xxhdpi/ic_settings_mobilenetworks.png