fix to backup and fix max client

in  this version, you can backup postgresql

pgadmin/Dockerfile

-FROM chorss/docker-pgadmin4
+FROM fenglc/pgadmin4
 
-MAINTAINER Bo-Yi Wu <appleboy.tw@gmail.com>
+MAINTAINER Huadong Zuo <admin@zuohuadong.cn>
+
+# user: pgadmin4@pgadmin.org
+# password: admin
+# pg_dump in  "/usr/bin"
+# backup in "/var/lib/pgadmin4/data/storage/pgadmin4/"
 
 EXPOSE 5050