adding mssql-cli example dockerfile

linux/preview/examples/mssql-cli/Dockerfile

@@ -0,0 +1,18 @@
+FROM ubuntu:16.04
+
+# apt-get update and install required utilities
+RUN apt-get update && apt-get install -y \
+    curl apt-utils apt-transport-https debconf-utils gcc build-essential g++-5\
+    && rm -rf /var/lib/apt/lists/*
+
+# adding custom MS repository
+RUN curl https://packages.microsoft.com/keys/microsoft.asc | apt-key add -
+RUN curl https://packages.microsoft.com/config/ubuntu/16.04/prod.list > /etc/apt/sources.list.d/mssql-release.list
+
+# Update the list of products
+RUN apt-get update
+
+# Install mssql-cli
+RUN apt-get install mssql-cli -y
+
+CMD ["/bin/bash", "-c", "sleep infinity"]