Move packaging scripts for docker and appimage into subdirectory.

- De-clutter the project root directory.

packaging/appimage/AppRun

@@ -0,0 +1,26 @@
+#!/bin/sh
+
+
+# This is a modified version of the AppRun made by AppImage's meta/Recipe.
+
+
+set -e
+
+
+HERE="$(dirname "$(readlink -f "${0}")")"
+export APPDIR="${HERE}"
+export PATH="${HERE}"/usr/bin/:"${HERE}"/usr/local/bin/:"${PATH}"
+export UNION_PRELOAD="${HERE}"
+export LD_PRELOAD="${HERE}/libunionpreload.so"
+export LD_LIBRARY_PATH="${HERE}"/usr/lib/:"${HERE}"/usr/lib/i386-linux-gnu/:"${HERE}"/usr/lib/x86_64-linux-gnu/:"${HERE}"/usr/lib32/:"${HERE}"/usr/lib64/:"${HERE}"/lib/:"${HERE}"/lib/i386-linux-gnu/:"${HERE}"/lib/x86_64-linux-gnu/:"${HERE}"/lib32/:"${HERE}"/lib64/:"${LD_LIBRARY_PATH}"
+export PYTHONPATH=/usr/local/lib/python3.9/dist-packages:"${PYTHONPATH}"
+if [ -z $APPIMAGE_ENTER ]; then
+    EXEC=$(grep -e '^Exec=.*' "${HERE}"/*.desktop | head -n 1 | cut -d "=" -f 2- | sed -e 's|%.||g')
+    exec ${EXEC} $@
+else
+    if [ -z "$@" ]; then
+	exec /bin/bash
+    else
+	$@
+    fi
+fi