Fix remote file paths on Windows

Deployment is broken on Windows, because of the changes introduced in ceede908f5bbeaf53fb729ee2e3d1ae32d9c46ca. On Windows, path.normalize() produces file URIs with backslash separators (i.e. `"path1\path2\file.fl"`), whereas the FTP spec requires to use forward slashes as directory separators.

This at very least uploads files into wrong directories and at most produces "wrong filename" errors on the FTP server trapping the upload process in a vicious continuous loop.

  * Add `_constructRemotePath` method that replaces all occurrences of backslashes to forward slashes in a given string.
  * Call `_constructRemotePath` upon file upload and revision file check.