AzerothCore complete Docker solution

Check https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker for all details.

docker/build/Dockerfile

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+FROM ubuntu:bionic
+
+RUN apt update && apt install -y git cmake make gcc g++ clang libmysqlclient-dev libssl-dev libbz2-dev libreadline-dev libncurses-dev libace-6.* libace-dev
+
+ADD .git /azerothcore/.git
+ADD deps /azerothcore/deps
+ADD conf/config.cmake.dist /azerothcore/conf/config.cmake.dist
+ADD src /azerothcore/src
+ADD CMakeLists.txt /azerothcore/CMakeLists.txt
+
+RUN cd azerothcore; \
+    mkdir build; \
+    cd build; \
+    cmake ../ -DCMAKE_INSTALL_PREFIX=/azeroth-server -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DTOOLS=0 -DSCRIPTS=1; \
+    MTHREADS=`grep -c ^processor /proc/cpuinfo`; MTHREADS=$(($MTHREADS + 2)); \
+    make -j $MTHREADS; \
+    make install -j $MTHREADS;

docker/build/README.md

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+# AzerothCore Dockerized Build
+
+The AzerothCore Build Dockerfile is not meant to create containers, it is a stage that both the [authserver](https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker/authserver) and the [worldserver](https://github.com/azerothcore/azerothcore-wotlk/tree/master/docker/worldserver) docker images will use.
+
+Note: every time you update your AzerothCore sources, you **must** build again this image and the authserver & worldserver images to get the new version on your docker containers.
+
+*For more information about Docker multi-stage builds, refer to the [docker multi-stage builds doc](https://docs.docker.com/develop/develop-images/multistage-build/).*
+
+# Usage
+
+To build the container image you have to be in the **main** folder of your local AzerothCore sources directory.
+
+```docker build -t azerothcore/build -f docker/build/Dockerfile . ```