Rewrite StmtInserter

[ajthinking]

The method insertStmts method automatically sorts the nodes in a strange way. Typically using ->add() will prepend the node among its equals. So the new use statement below will come out in the top:

PHPFile::load(User::class)
    ->add()->use(['Add\This']);

Improvements

• ability to bypass automatic sorting (for example put properties AFTER methods if you for some reason want to)
• ability to prepend and push among equals
• sorting styles (by length, alphabetically)