Incremental OTA support

[anonymix007]

Closes #19

This is an initial poorly tested implementation supporting some InstallOperation types for delta payloads: BSDIFF, SOURCE_BSDIFF, BROTLI_BSDIFF and PUFFDIFF. Others (ZUCCHINI, LZ4DIFF_BSDIFF and LZ4DIFF_PUFFDIFF) could be implemented similarly. This is probably broken for many payloads, so any help is welcome.

Usage:

./payload-dumper-go -d extracted_v340 -o extracted_v346 payload_346.bin

extracted_v340 directory contains full images, output extracted_v346 will contain images after applying incremental payload_346.bin

[snowwolf725]

I tried to compile but found that it failed due to the lack of relevant libraries.

[anonymix007]

@snowwolf725 There are compilation instructions in the second commit:

Compilation

Linux and OSX

git submodule update --init --recursive
go generate chromeos_update_engine/update_engine.go 
go build .