Lockscreen Targets: Icon Revamp

Adjust the size of custom app icons and resize and round the corners
of gallery icons for a more uniform look.

Before http://imgur.com/cTOqdwX

After http://imgur.com/EKAeFiw

Change-Id: Ibcca275eb0ae946775773a8c8217b6508da10e5b

Conflicts:
	policy/src/com/android/internal/policy/impl/keyguard/KeyguardSelectorView.java