* Update Docker.md
Add link to enabling docker buildkit. Add note to remember to clone submodules.
* Remove unpacked client option
Unpacked client does not have required directories/files (e.g. /versions/trunk.txt) and thus the packed client is required.
* Add note about renaming CDClient.fdb
DarkflameSetup will fail because it cannot find cdclient.fdb. However, CDClient.fdb exists. Renaming it fixes the issue.
* Remove extra "client"