Use github actions to perform continuous integration build on
ubuntu latest and gcc-10. (closes: #50)

We need to remove c++20 module in boost.ut. It fails to compile.

This patch enables to load and save irt file with position (a couple of float)
for each model (closes: #42).

This patch introduce a new file format. A couple of float is added in the model
definition after the identifier and before the dynamics name.

The "input-output" unit test is updated.

Re-introduce the sin_time_function in kernel and GUI.
(closes: #39).

Co-authored-by: Yves Nedelec <yves.nedelec@cerema.fr>