First release

I don't know going forward how much time I will have to continue working on this, but I believe that what I have is enough to deserve the first release. My little project of writing a parser and interpreter in PHP from scratch lives. Meet Polygen-PHP 1.0.0!

As far as I know, this should be compatible with all current Polygen grammar files. Please refer to the official Polygen documentation for guidance on how to write a grammar.