Improved U-Boot splashes

There has been interest to overhaul development on the Amazon Otter and
I'd like to contribute for it, Hashcode had recently posted some mockups
of an improved bootlogo and I'd want to improve on it

This pull request includes UBoot splashes for the Fastboot, Low Battery
and Init splash screens

I have not found documentation to create a U-Boot friendly compressed
rle image so these are on uncompressed rle format (I couldn't even look
at them to take a look at the orientation so this is completly untested,
fastboot is unlinked)