Auto-resize lock screen - fixes Layout issues for MDPI/NODPI and is still compatible with HDPI

This was submitted by jokeyrhyme at http://code.google.com/p/openeclair/issues/detail?id=179

Changes:
--- core/res/res/layout/keyguard_screen_sim_pin_portrait.xml ---
Okay, I have got the final version of the SIM Unlock screen done. I've made the
barest modifications to get the keypad to scale, and reduced the margin above the
code display just slightly. I've reordered the XML so that the Emergency Button is
drawn at the bottom, and then the keypad is stretched between it and the code
display.

--- core/res/res/layout/keyguard_screen_tab_unlock.xml ---
I took a look at the Slide Unlock screen too (keyguard_screen_tab_unlock). The only
change necessary was the placement of the Emergency Call button. Instead of being
placed over the unlock tab, it is now anchored to the bottom-centre of the screen.