Projectlayer: float/int bug in default config on windows

Hi,

I just resolved a bug whereby default settings for project_x and project_y were floats, and this cause ValuErrors when loading from windows (because there is a different config file for windows it seems).

Commits 34c0fb9 and c4ca91a have the actual fix, plus a guard for existing config that already has a float defined.

Best regards,
Gary