Let codegen tool generate multiple files

[ciaranmcnulty]

Both the PHP and Java implementations use csplit to split the generated code across multiple files.

This should be made a feature of codegen.rb in a future refactor

[luke-hill]

I just saw this recently. I am currently refactoring the codegen.rb file completely after having Rien show me how to use csplit on the ruby files to get them all in different ones.

The entire process for using csplit only took around 30-45mins of pairing. I'd be happy to pair up with you if you'd like. I'm not really sure how the codegen could do it, given it loads everything into one big hash / set, and then iterates through them.

We could completely rewrite the codegen.rb logic to do it from first principles I suppose. But that kind of large scale refactor wouldn't be easy to do part-time.

[luke-hill]

#228