Use simple invocation type instead of forking daemon
Add alternative unit file for /usr/local installs
Add /opt/ systemd unit variant
Fix comments
Add 3GB memory limit to systemd unit
Restore newlines at end of systemd unit files
Remove "via official sources" comment from the opt systemd unit file
Use term "variant" instead of "variation" since the former is more
specific and correct for this context
Correct dogecoin package directory from "dogecoind" to "dogecoin"
Use tarball bin path
Co-authored-by: Patrick Lodder <patricklodder@users.noreply.github.com>