IVE: Fix QProcess call in ModelCheckingWindow

• In ModelCheckingWindow QProcess::execute() is still using the Qt5 API. A split into command and arguments is needed.
• Check the whole code for more old QProcess usages
  • extprocmonitor.cpp
  • asn1reader.cpp
  • tmc::converter.cpp
  • sdltopromela::converter
  • verifier.cpp
  • simulinkimporterplugin.cpp
• Make the ASN.1 highlight work (install .xml files, even if asn plugin is disabled)
  • QtCreator4.8 uses share/qtcreator/generic-highlighter
  • QtCreator8 uses share/qtcreator/generic-highlighter/syntax
• Update Readme.md to point to quickstart.md
• Remove unused script files (shell script in "scripts" folder)