added further test: require_isisscripts_loads_without_additional_modules.sl

This test checks if the isisscripts can be loaded without any other
modules available. Due to this change, some routines had to be
modified in order to meet the new standards.

	modified:   src/fitting/mpi_fit_pars.sl
	modified:   src/fitting/parameters/conv_reflXill.sl
	modified:   src/slang/misc/storevar.sl
	new file:   test/require_isisscripts_loads_without_additional_modules.sl