Use external Hatanaka library for crx2rnx and rnx2crx

[valgur]

Hi! I recently created a carefully packaged and wrapped version of the RNXCMP tools in Python as the Hatanaka library. It simplifies the installation and usage of the tools and also makes sure any errors are raised as proper exceptions and warnings as Python warnings. It can also take care of the .gz/.Z compression usually applied on top of Hatanaka compression, but I did not add that to the PR.

I thought you might find the library useful as well.