Add all license files to better assist tool vendors in distribution of source or binary files

[beutlich]

This PR adds the license files of both the own MA work and the dependent third-party open-source licenses. This in preparation of MCP-0029 to better support tool vendors when distributing derived work of the MSL.

Have a look at

• the accompanying documents of MCP-0029 in MCP-0029: Add License Annotation for External Libraries and Include Files ModelicaSpecification#2217,
• Vendor Neutral Modelica Annotation Prototypes in MSL #849 if we even want to add the __ModelicaAssociation_License annotation as proposed by MCP-0029,
• Analysis of third-party licenses of C-Sources #2253 for an analysis of the licenses,
• FMUs must contain all relevant license information fmi-standard#417 for an important use-case

I called the license file for ModelicaFFT.[ch] LICENSE_ModelicaKissFFT.txt. Maybe we should have it consistent and rename the source files, too.

[HansOlsson]

Looks good as is.
However, looking at the licenses I think we should modify MCP0029, and thus I don't believe we should add the license-annotation yet. (Will make specific comment.)