FIXED_LEN_BYTE_ARRAY support

I have implemented FIXED_LEN_BYTE_ARRAY support (Issue #100). This implementation is working for core Parquet, Avro support, and Pig support. For Parquet Pig support, FLBA fields can be read and is written out as bytearray fields.

I am still working on plumbing FLBA support through to Hive, but because the change set is getting rather large, I've decided to send this pull request now and send a separate PR for Hive support later.

@tomwhite - There are parquet-avro changes here. Can you please take a look and let us know if you have any feedback on these changes?

Thanks!