Add UID/GID option and custom config base for docker

Closes #13

docker/run.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+
+function fixperms {
+    chown -R $UID:$GID /var/log /data /opt/maubot
+}
+
+cd /opt/maubot
+
+if [ ! -f /data/config.yaml ]; then
+	cp docker/example-config.yaml /data/config.yaml
+	mkdir -p /var/log /data/plugins /data/trash /data/dbs
+	echo "Config file not found. Example config copied to /data/config.yaml"
+	echo "Please modify the config file to your liking and restart the container."
+	fixperms
+	exit
+fi
+
+mkdir -p /var/log/maubot /data/plugins /data/trash /data/dbs
+#alembic -x config=/data/config.yaml upgrade head
+fixperms
+exec su-exec $UID:$GID python3 -m maubot -c /data/config.yaml -b docker/example-config.yaml