Add license files are required by REUSE and add license
files as reuqired by REUSE.
Please note the following points:
- all links to dead webpages were removed from license statements
- I do not think that the ID markers are still needed, which are contained in several license headers (@mirko: are they still needed?)
- In both src/examples/ItemdDelegate.cpp/.h there is a license clarification that this file may be linked with any version of Qt. I do not see that this license clarification is needed, because that automatically comes with the LGPL. (@all: what is your opinion?)