Move index.php from project root, init composer, get rid of random includes and define statements

[grbnshchkv]

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[grbnshchkv]

@Md-Cake please, have a look when you have time.

Basically, I'm going to rewrite most of the codebase to make the project compatible with modern PHP versions, get rid of outdated dependencies, make it testable, etc.

I already tried to do so in another branch (https://github.com/Grebenschikov/codeisok/tree/codeisok_2.0) but there are too many changes at once, and it's very hard to keep it in sync with changes in master, so I decided to do it iteratively (and without breaking changes as much as possible).

There are not many changes in this PR since @makinfieva already moved all classes to the namespaces.

So actually, in this PR I just cleaned up a bit root folder (and moved all web-related staff to the «public» folder) and got rid of floating includes and defines in the root namespace. And initialized composer for further changes.