Moved code dealing with locating configuration files from `ConfigParser` to `ConfigFinder`
Added constants for config folder and config file names
Added `CeylonConfigFinder` as an easy-to-use shortcut for a `ConfigFinder` dealing with the Ceylon "config" file
Updated all code that was using that static locator methods in `CeylonParser` to now use either `CeylonConfigFinder` or the `ConfigFinder`