Solve copyright issues for 3rd-party scripts and tools

As a corollary of #99, I run across a few issues:

* [cmake/find-modules/tcbrindle_sdl2-cmake-scripts.md#licence](https://github.com/asrob-uc3m/robotDevastation/blob/dbc19de5f1d72b71b16212242e68672cc9d38736/cmake/find-modules/tcbrindle_sdl2-cmake-scripts.md#licence): "The original scripts, and my changes, are released under the two-clause BSD licence." -> **missing BSD 2-clause license file** (compare [cmake/Copyright.txt](https://github.com/asrob-uc3m/robotDevastation/blob/dbc19de5f1d72b71b16212242e68672cc9d38736/cmake/Copyright.txt))
* [cmake/find-modules/FindZBar.cmake](https://github.com/asrob-uc3m/robotDevastation/blob/dbc19de5f1d72b71b16212242e68672cc9d38736/cmake/find-modules/FindZBar.cmake): "Copyright (C) 2010 blah blah. All rights reserved." -> **uh-oh**

Start by reading cmake/find-modules/tcbrindle_sdl2-cmake-scripts.md, cmake/Copyright.txt, and cmake/find-modules/FindZBar.cmake, focusing on the cited license and copyright statements. Add the missing BSD 2-Clause license file and resolve the licensing or attribution issue in FindZBar.cmake, documenting the final status clearly.

Written by the indexing model from the issue text.