Describe the file structure of a .bloom filter

[brainstorm]

@tzcoolman, could you please briefly document the binary structure of a .bloom filter generated with FACS? I could greatly help debugging issues such as #122 and possibly implement better serialization/compression formats in the future.

Something like this would help a lot:

http://kas1e.mikendezign.com/aos4/docs/hack1/image_3_full_file.png

Comments in build.c would be super welcome too!

[tzcoolman]

@brainstorm
Just saw it. Will do