adding the original kba.thrift file that defines streamcorpus v0_1_0 so
that we can work with old objects, e.g. to transform them to new objects.

Also updating __init__.py to expose all the things that we want in __all__
Adding md5_hexdigest property to streamcorpus.Chunk, so we can get the
hash and use it in file names.  Bringing in the decrypt_and_uncompress
and compress_and_encrypt tools from KBA 2012, and also exposing the
v0_1_0 thrift objects that we used in KBA 2012.