The SNIO and SMETIO plugins now use METEOPATH for both inputs and outputs. This is more consistent with other plugins and usage.

Some unused variables/methods have been removed from BufferedIOHandler (namely, the "buffer_always" functionality).

A first implementation of fileExists() and readDirectory() for Windows has been written. This has not yet been tested (even for compilation) since it requires Visual C++. This moves forward to address issues 143 and 144