Removed libSBML finding code; changed LIBNUML_LIBRARY into LIBNUML_PREFIX for disambiguation purposes.
Added COPASI as a biopredyn submodule in Prototype/src
Updated libsedml to the latest version.
Changed LIBSBML_LIBRARY into LIBSBML_PREFIX in order to avoid overlapping with the LIBSBML_LIBRARY variable used in other dependencies using libSBML (such as COPASI, libsedml, etc).
Removed libSBML finding code in libsbmlsim CMake files.