Introduce boolean self.openAPackage

Checks Modelica Path, if it contains a package.mo the package should be
opened. If there is no package.mo, openAPackage goes False
Add variable self.scriptToOpen

Changes adds runScript to simulate() if ModelicaPath includes a .mos file
and no package.mo
Move script of package check to simulate()
Move check package or script to setPackagePath
Minor clean-up