The add-on code was copy-pasted from other addons and used the GPL v2
license, whereas by accident the LICENSE text file had the GNU "Affero" GPL
license v3 (instead of regular GPL v3).
This is now all streamlined, and all code is licensed as "GPL v3 or later".
Furthermore, the code comments just show a SPDX License Identifier
instead of an entire license block.
Add `crosspath.ToNative(path)`, which returns the path with platform-
native path separators. This is meant for use in the Worker, to convert
paths before attempting to use them.
Both Go's standard `path` and `path/filepath` packages are too limiting to
work well for Flamenco. The former assumes Linux/POSIX paths, the latter
only works with platform-native paths. Neither can work with Windows paths
on Linux, or Linux paths on Windows.
