Replace envuidgid with setuidgid and make run files executable (#203)

* envuidgid only sets environment variables $UID and $GID causing electrum_server to fail at https://github.com/kyuupichan/electrumx/blob/master/electrumx_server.py#L35-L37
Replaced envuidgid with setuidgit which runs electrum_server with the specified uid/gid

* Make run files executable

contrib/daemontools/run

@@ -1,3 +1,3 @@
 #!/bin/sh
 echo "Launching ElectrumX server..."
-exec 2>&1 envdir ./env /bin/sh -c 'envuidgid $USERNAME python3 $ELECTRUMX'
+exec 2>&1 envdir ./env /bin/sh -c 'setuidgid $USERNAME python3 $ELECTRUMX'