Move all SearchCar query stuff to SearchCar/ dir.

This creates a more examplary file structure to copy in case a
new query needs to be added.
Create a facade for all the SearchCar classes.

Move all SearchCar-specific code from index.php into that class.

Simplified the index.php significantly and provides a better
template for extending the system with new query types.
Remove hard-coded INI file name from DbFactory.

Also suppress warnings from parse_ini_file function - we only want
the exception.
Add README file.