Create Base and docker file for EdgeHub. (#922)

edge-hub/docker/linux/arm64v8/Dockerfile

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+ARG base_tag=1.0.0-preview010-linux-arm64v8
+FROM azureiotedge/azureiotedge-hub-base:${base_tag}
+
+ARG EXE_DIR=.
+
+WORKDIR /app
+
+COPY $EXE_DIR/ ./
+
+# Expose MQTT, AMQP and HTTPS ports
+EXPOSE 8883/tcp
+EXPOSE 5671/tcp
+EXPOSE 443/tcp
+
+USER edgehubuser
+ENV OptimizeForPerformance false
+ENV MqttEventsProcessorThreadCount 1
+CMD echo "$(date --utc +"[%Y-%m-%d %H:%M:%S %:z]"): Starting Edge Hub" && \
+    exec /usr/bin/dotnet Microsoft.Azure.Devices.Edge.Hub.Service.dll

edge-hub/docker/linux/arm64v8/base/Dockerfile

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+ARG base_tag=3.0-runtime-bionic-arm64v8
+
+FROM microsoft/dotnet:${base_tag}
+
+# Add an unprivileged user account for running Edge Hub
+RUN useradd -ms /bin/bash edgehubuser
+ENV EdgeHubUser=edgehubuser
+
+RUN apt-get update && \
+    apt-get install -y libsnappy1v5 && \
+    rm -rf /var/lib/apt/lists/* && \
+    ln -s /lib/aarch64-linux-gnu/libdl.so.2 /usr/lib/aarch64-linux-gnu/libdl.so.2 && \
+    ln -s /lib/aarch64-linux-gnu/libdl.so.2 /lib/aarch64-linux-gnu/libdl.so && \
+    ln -s /lib/aarch64-linux-gnu/libdl.so.2 /usr/lib/aarch64-linux-gnu/libdl.so && \
+    ln -s /lib/aarch64-linux-gnu/libc.so.6 /usr/lib/aarch64-linux-gnu/libc.so.6
+
+COPY  librocksdb.so /usr/lib
+
+# add the CAP_NET_BIND_SERVICE capability to the dotnet binary because
+# we are starting edge hub as a non-root user
+RUN setcap 'cap_net_bind_service=+ep' /usr/share/dotnet/dotnet