Add clang-format-all.sh to format all project sources

clang-format-all.sh

+ROOT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+SRC_DIR=${ROOT_DIR}/src
+CLANG_FORMAT=${CLANG_FORMAT:-clang-format}
+
+# Double clang-format, as it seems that one pass isn't always enough
+find ${SRC_DIR} -iname "*.h" -o -iname "*.cpp" | xargs ${CLANG_FORMAT} -i -style=file
+find ${SRC_DIR} -iname "*.h" -o -iname "*.cpp" | xargs ${CLANG_FORMAT} -i -style=file
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