Add more useful applications

Author: js-jslog

Dockerfile

@@ -38,6 +38,9 @@ RUN apt-get update && apt-get install -y -q --no-install-recommends \
         git \
         software-properties-common \
         ssh \
+        mysql-client \
+        python \
+        postgresql postgresql-contrib \
     && rm -rf /var/lib/apt/lists/*
 
 # Install vim and customise