Add option to supply your own decode/encode tables

[KaDw]

Now tables are part of the tool, they are embedded as static arrays. There are a couple of problems with that:

• they are not the same for every .pk file that was released.
• if any of the table changes new version of pk-crypt-rs has to be compiled and released

The only drawback might be that the tool will no longer be single executable

It would be nice to have them on the side eg. in utils/ directory and supply them using -t --tables option.