#7 Localized separator bug

[Tomas Björklund]

The application will crash at any sites where "." is'nt
used as a decimal separator.

The positions in TileFile.xml are expressed as floats, and
when the parser tries to use the Convert class on them,
when reading the XML, and exception is thrown.

Workaround ... well, for the moment you have to set the
separator in windows settings.

This should of course be coded in a locale-neutral way.