v0.28

• replaced Trie.h and TreeHash.h/.cxx by Unicode aware variants
• refactoring in StringOps, weeding split* functions. Added join() function
• added functionality to Unicode.cxx, like split* and join() and converters
  also a dedicated getline() function to directly read UnicodeString's
• several refactoringsin CommandLine.cxx
• added a fnction to CommandLne.cxx to remove a section
  (#24)
• adapted runtest.cxx to new and changed functions
• added new 3.10.3 version of nlohmann JSON library
• fix for: https://gitlab.alpinelinux.org/proycon/aports/-/jobs/452481#L1005