Add arm-x19 template folder

I adapted the build scripts a tiny bit to create arm-x19 packages. For that to work you'll need my other pull request for the plex-media-server-distro-scripts repository.

I do realize that you just disabled QNAP in your build process but I thought I create the request anyway :)

Have a good day

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... and move shared/plex.sh to x86_template
since that script won't work on QNAP arm-x19