Clean up source headers and NOTICE file

Description

See https://groups.google.com/d/topic/sesame-devel/j81ISui6kqk/discussion

Consensus is to get rid of copyright headers in source code altogether and just include an (Apache-style) license header. Copyright notices for each contributor are added to the NOTICE.txt file in the distribution.

Environment

None

Status

Assignee

Jeen Broekstra

Reporter

Jeen Broekstra

Labels

None

Fix versions

Priority

Major
Configure