Add temporary script to filter license notices

Add a script to replace our previous per-source license notices with a
much simpler notice.  This will be used in a following commit and then
removed.

Change-Id: I63911c5b21bab6c198f7f65f7facffd6a1df405c

filter-notices.bash

+#!/usr/bin/env bash
+
+# Filter scripts.
+
+regex='#=====================*
+(# KWSys - Kitware System Library
+)?(# Copyright.*
+)*#
+# Distributed under the OSI-approved BSD License \(the "License"\);
+# see accompanying file Copyright.txt for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=====================*(
+# \(To distribute this file outside of CMake, substitute the full
+#  License text for the above reference.\))?
++'
+files="$(git ls-files -- | egrep -v ' ' | xargs pcregrep -M -l "$regex")"
+
+
+if test "x$files" != "x"; then
+  sed -i '1 i# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying\
+# file Copyright.txt or https://cmake.org/licensing#kwsys for details.\
+
+' $files
+
+  perl -i -0pe "s/$regex//" -- $files
+fi
+
+# Filter C and C++ sources.
+
+regex='\/\*=======================*(
+  .*)+
+
+  Distributed under the OSI-approved BSD License \(the "License"\);
+  see accompanying file Copyright.txt for details.
+
+  This software is distributed WITHOUT ANY WARRANTY; without even the
+  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the License for more information.
+=======================*\*\/
++'
+
+notice='\/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https:\/\/cmake.org\/licensing#kwsys for details.  *\/
+'
+
+git ls-files -z -- | xargs -0 perl -i -0pe "s/$regex/$notice/g"