Blender and FFmpeg were run in the same way, using copy-pasted code. This
is now abstracted away into the CLI runner, which in turn is moved into
its own subpackage.
No functional changes.
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.
Some parts of Flamenco had a Command consist of "name + settings", and
other parts used "type + parameters" (with the same semantics). This is
now unified to "name + parameters".
