Remove the version number from the directory name of the Modelica source code

[jowr]

Remove the version number from the directory name of the Modelica source code directory, because that requires changing all the file names every time a new version is released. We could make without it, or possibly change the build script to copy all the required files on a build directory where the version number is added to the Modelica directory name, if that is not too difficult

[casella]

Fixed on the dynamiclib branch, will be merged to master prior to the next release