Replace PSR-4 with classmap autoloader

[j3j5]

I am once again asking for your support trying to fix #253.

I think this is the best approach (as discussed on the phpdocparser issue ) and it's also much less disruptive than the renaming of all files done in #338.

I've tested the code with this repo, but please, test it yourselves to make sure I don't break anything else again 😛

Hope this is the good one!

[Kharhamel]

This looks really easy. I need to think about how to test this on a bigger scale. I will probably create a beta for this but this means i need to merge this into master.

[j3j5]

Yeah, please double check that I didn't miss any class. The only downside is that if a new class is ever added that doesn't fall in the folders (new exceptions will be fine), it'll need to be added manually. I don't think there will be another case like Datetime in this library, but something to be aware of.

[szepeviktor]

@j3j5 I think #348 is the ultimate solution.

[j3j5]

As I mentioned on previous attempts, I don't mind which approach we use, I just want to get rid of the error so whatever is easier/better for the actual maintainers :)

[Kharhamel]

@szepeviktor didn't propose his pull request yet, so I am going to merge this for now and create a beta to test it. Is it ok with you @j3j5?

[j3j5]

Yeah, I mean, it should fix the problem for now (hopefully) and later we can go with the "final solution" if y'all like it better.