Add 1280x720@320dpi skin.

Also tweak some skins to provide more ram to the emulator
for better performance.

Change-Id: I89dcdb7a6a78d95132820db284c1fdfb6f82c6db
diff --git a/build/sdk.atree b/build/sdk.atree
index ad1d19f..c5d5798 100644
--- a/build/sdk.atree
+++ b/build/sdk.atree
@@ -79,7 +79,8 @@
 development/tools/emulator/skins/WVGA800   platforms/${PLATFORM_NAME}/skins/WVGA800
 development/tools/emulator/skins/WVGA854   platforms/${PLATFORM_NAME}/skins/WVGA854
 development/tools/emulator/skins/WSVGA     platforms/${PLATFORM_NAME}/skins/WSVGA
-development/tools/emulator/skins/WXGA      platforms/${PLATFORM_NAME}/skins/WXGA
+development/tools/emulator/skins/WXGA720   platforms/${PLATFORM_NAME}/skins/WXGA720
+development/tools/emulator/skins/WXGA800   platforms/${PLATFORM_NAME}/skins/WXGA800
 
 # Platform SDK properties
 development/sdk/sdk.properties               platforms/${PLATFORM_NAME}/sdk.properties