Lockscreen targets: more unification

Don't hardcode pixel sizes, and use a shared method to derive drawable
inset.

Change-Id: I2adf9230c5aa8efadddd713c435b37af24e23115
Merge "Lockscreen targets: more unification" into cm-10.2
Merge pull request #5 from CyanogenMod/cm-10.2

Cm 10.2