Copy apache2 license text into fixlegal.py

Prepare to move the code under the Apache 2.0 license.
Adopt the Apache 2.0 license

Update 'meta/autofix/fixlegal.py' to apply the Apache 2.0 license to
all files.

Replace the contents of ./LICENSE with the Apache 2.0 license.

Test Plan:
Apply 'fixlegal.py' to all files
Visual examination of the diff and some changed files
$ ./precommit.sh
Remove MIT License from fixlegal.py