Move contents of _LICENSE dir to special files for auto discoverability

[Bomme]

Issue(s)
#1683

Description
As suggested by @alastair I moved the license statement to the top level directory so that it gets read by GitHub. Moreover, I created an ACKNOWLEDGMENTS file containing the licenses of the python dependencies as generated by pip-licenses.

I followed this recommendation:

ACKNOWLEDGMENTS File: ACKNOWLEDGMENTS or ACKNOWLEDGMENTS.txt or ACKNOWLEDGMENTS.md etc. is a file that describes related work, such as other projects that are dependencies, or libraries, or modules, or have their own copyrights or licenses that you want to include in your project.

Deployment steps:
None