Reduce themes to 5 and rely on scaling

This will significantly reduce theme maintainence and should be a
lot more sustainable over time. Eliminate most themes leaving only
5 remaining in 3 categores:
 * watch_mdpi: 320x320
 * portrait_mdpi: 480x800
 * portrait_hdpi: 1080x1920
 * landscape_mdpi: 800x480
 * landscape_hdpi: 1920x1200

Add handling to map the old DEVICE RESOLUTION to the new TW_THEME
build flag. New devices should specify a theme using the new
TW_THEME build flag using one of the 5 values from the list above.
Long term we will eliminate the use of the DEVICE_RESOLUTION flag
in favor of the new flag.

Change the way sliders render so that they completely follow the
placement="5". This will probably break some custom themes but is
necessary so that we can retain the aspect ratio on slider images
and still have them rendered at the center of the screen.

Add code to the console slideout button so that it can be centered.
Centering the slideout button allows us to keep the button at the
center of the screen when retaining aspect ratios on the image.

Add more retain aspect ratios for home, back, slideout, folder,
file, and lock screen images.

Change the way we build the top bar in TWRP. It is now mostly
drawn using fill objects and the TWRP logo is a separate image so
that we can retain its aspect ratio during scaling. Thanks to Mark
Norelus for providing the TWRP logo.

Change-Id: I801a7b3163cad9ef353461f4c327690a9ccbb3aa
diff --git a/gui/devices/landscape/res/landscape.xml b/gui/devices/landscape/res/landscape.xml
index c05ab50..0a907cb 100644
--- a/gui/devices/landscape/res/landscape.xml
+++ b/gui/devices/landscape/res/landscape.xml
@@ -80,7 +80,7 @@
 		<style name="slider">
 			<text>Swipe to Confirm</text>
 			<font resource="font" color="%text_color%" />
-			<placement x="%slider_x%" y="%slider_y%" placement="5" />
+			<placement x="%center_x%" y="%slider_y%" placement="5" />
 			<resource base="slider" used="slider-used" touch="slider-touch" />
 		</style>
 
@@ -2771,7 +2771,7 @@
 
 			<object type="image">
 				<image resource="unlock-icon" />
-				<placement x="%lock_x%" y="%lock_y%" />
+				<placement x="%center_x%" y="%lock_y%" placement="4" />
 			</object>
 
 			<object type="slider">