Update Calculix adapter to 2.16 from 2.15

[Eder-K]

After the version upgrade of the Calculix adapter to Calculix v2.16 is implemented, the Dockerfile pertaining to the Calculix adapter needs to be updated:

systemtests/adapters/Dockerfile.calculix-adapter

Lines 28 to 33 in dfca1db

	RUN curl -s http://www.dhondt.de/ccx_2.15.src.tar.bz2 | tar -xj
	ARG branch=develop
	RUN git clone --branch $branch https://github.com/precice/calculix-adapter.git
	WORKDIR calculix-adapter/
	# specify proper locations of libraries
	RUN sed -i -e 's|CCX\s\+=.*|CCX = /home/precice/CalculiX/ccx_2.15/src|g'\

[Eder-K]

Update was performed in #231.