Change license to Apache-2.0 with LLVM exceptions (#3793)

* Change license to Apache-2.0 with LLVM exceptions

* docs : add NOTICE file for legal disclaimer

* docs: Add CHANGES for license change only release 7.0.1

* Update NOTICE

* Update NOTICE

---------

Co-authored-by: Eric J Bohm <ebohm@illinois.edu>
Co-authored-by: Abhinav Bhatele <bhatele@illinois.edu>

Author: 3 people

CHANGES

@@ -1,6 +1,20 @@
 This file describes the most significant changes. For more detail, use
 'git log' on a clone of the charm repository.
 
+===============================================================================
+What's new in Charm++ 7.0.1
+================================================================================
+
+This is a change license only release, with the following change:
+
+Highlights:
+
+- The License has changed to Apache 2.0 with LLVM exception.  This
+  change to a popular Open Source license is intended to simplify use,
+  collaboration, and greater community involvement in the development
+  of Charm++. The NOTICE file contains the pertinent disclaimers.
+
+
 ================================================================================
 What's new in Charm++ 7.0.0
 ================================================================================