get relative path of File 'f' with respect to 'home' directory example :
home = /a/b/c f = /a/d/e/x.txt s = getRelativePath(home,f) =
../../d/e/x.txt
Parameters: home - base path, should be a directory, not a file, or it doesn'tmake sense Parameters: f - file to generate path for path from home to f as a string