Prevents failure of the installation of jellyfin-web dependencies due
to the NodeJS version in EPEL being too old. v8 might be a little
conservative but is the earliest compatible version. Instead of using
their repo to install Yarn, use the new nvm binary to install Yarn, thus
forcing it to use the updated NodeJS version.
This performs a lot of bugfixing and general cleanup to the
Fedora/CentOS builds, including moving the create_tarball into the
docker-build.sh script, remove some old long versions from the spec
file, correcting several bugs with the Docker environment including
splitting them into more discrete layers, and finally making sure
jellyfin-web is included properly in the RPM.
