(NFC) (dev/core#878) Simplify copyright header (D7)

[totten]

Overview

This implements https://lab.civicrm.org/dev/core/issues/878 and aims to reduce git-noise.

Before

• The standard header used on most files includes a copyright declaration - along with a version number, range of years, summary of the license terms, and link for details. The headers periodically require a trivial update when a new year comes.

After

• The standard header used on most files includes a copyright declaration - along with a very brief license summary and link for details. The headers no longer require a trivial update when a new year comes.

Comments

As you can see in 878, the comparable headers among other reputable projects are varied. They (almost always?) include the copyright declaration and some reference to the license terms; but they differ on whether to include specific version numbers and years in the declaration. However, this means that there are good precendents (such as Google's Angular and Facebook's React) which use a convention similar to this updated one.

This PR only changes files which already use the standard header (modulo trivial formatting). The bulk of the switch was performed with https://gist.github.com/totten/85d368a512f7dcda9319dfb57a0f8ecf

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).