Closes #95 Update trivadis/mktools Docker image

• new Dockerfile to produce trivadis/mktools with tags "2.0" und "latest" (published on Docker Hub)
• upgraded config from Materials for MkDocs v4 to v5 (mkdocs.yml, header.html)
• using "pymdownx.highlight" plugin including superfences and inlinehilight. This plugin is the successor of codehilite. See https://squidfunk.github.io/mkdocs-material/reference/code-blocks/#highlight and https://facelessuser.github.io/pymdown-extensions/extensions/highlight/ for details. All pymdown extensions can be used with the mktools Docker image.
• fixed issues based on new Material for MkDocs v5.5.14 und wkhtmltopdf v0.12.6
  • extra.css: various fixes due to new "@media print" defaults in Material for MkDocs v5 and use of CSS syntax that is not supported in wkhtmltopdf (or its tooling). Some changes due to replacement of codehilite.
  • genpdf.sh: use "linenums_style: table" for code, increase timeout, allow local file system access, disable smart shrinking
  • toc.xsl: new sizes due to disable smart shrinking
• fixed wrong shebang in shell scripts (#/bin/bash instead of #!/bin/bash)