Code is now organized by api version. So formatting has moved to
the api.v1 module. Instead of holding a separate ResultFormatter
object per result format, simply move the functions to the
formater collector and hand in the requested format as a parameter.
Thus reorganized, the api.v1 module can export three simple functions
for result formatting which in turn makes the code that uses
the formatters much simpler.
Use a directory for the submodule where the __init__ file contains
the public API. This makes it easier to separate public interface
from the internal implementation.
Check if the API script exists on the expected location before
running php-cli. This way we can add a useful hint about the
project directory.
Fixes#2513.
