brotlidump.py: disassemble brotli file (revisited) (#314)

* Create brotlidump.py

Sorry, I am a newbie. I couldn't find my file anymore when I wanted to edit it. Hope I don't waste your time.

* Fixed a bug where it couldn't read its own compression.

The problem was that a prefix code ending with a 16 "repeat" didn't realize the table was full already.
Also minor bug fixes, comments and stuff.

* Major refactoring

Rewrote almost everything.
Now can dump its own compression.

* Now more or less complete

Appears to handle all files completely (including metablock data).
Used as inspiration for the the hex example (see makehexexample.py)