DOC: enhance documentation and add tutorials

src/doc/getting_started/helloworld.md

src/doc/getting_started/helloworld.rst

src/doc/getting_started/prerequisites.md

src/doc/getting_started/prerequisites.rst

src/doc/index.rst

src/doc/tutorials/index.rst

src/doc/tutorials/parameterfile.rst

src/doc/tutorials/scifolder.rst