Add half-resolution boot animations for low-end devices

On low-end devices, the current 48 fps boot animation can use more than
50% of CPU time, and if the texture cache is enabled, a majority of main
memory as well.  For these devices, add half-resolution variants of the
lower-resolution boot animations which display 2x upscaled -- this
greatly speeds the boot process and makes the boot animation run more
smoothly.

Change-Id: I0140616ca38c52a06dd4622f1c20a9ca0da95f4b
Merge "Add half-resolution boot animations for low-end devices" into cm-11.0
cm: Add Trebuchet back to the build

Change-Id: Icbb6267a547e4022c6fc5382a33ba75e257006d9
cm: Add Galaxy S4 Mini maintainer

Change-Id: I7580e9e89f24eca96e5d4b76d71dc4a3b8b41816
Customize build