Fix: allow specifying sbml model with file extension. Otherwise there is no way for import when there is a .xml and .sbml file in the same folder.
Fix: allow specifying sbml model with file extension. Otherwise there is no way for import when there is a .xml and .sbml file in the same folder.

AMICI-developer/AMICI,AMICI-developer/AMICI,FFroehlich/AMICI,FFroehlich/AMICI,AMICI-developer/AMICI,AMICI-developer/AMICI,FFroehlich/AMICI,FFroehlich/AMICI