[RFC] Splitting PHP parser into multiple single parser classes

Extract multiple parser classes from `UAParser\Parser` to allow standalone usage.

What do you think?


## TODO
- [x] Extracting parsers
- [x] Deprecate passing a filename to the constructor of `UAParser\Parser` and introduce static factory method `UAParser\Parser::create(string $file = null)` so that all parser constructors take arrays of regexes
- [x] Updating docs