[#303] change SWATmodelParameters metadata elements from required to optional
[#303] change SWATmodelParameters metadata elements from required to optional

FescueFungiShare/hydroshare,RENCI/xDCIShare,ResearchSoftwareInstitute/MyHPOM,hydroshare/hydroshare,RENCI/xDCIShare,hydroshare/hydroshare,ResearchSoftwareInstitute/MyHPOM,hydroshare/hydroshare,FescueFungiShare/hydroshare,RENCI/xDCIShare,ResearchSoftwareInstitute/MyHPOM,hydroshare/hydroshare,RENCI/xDCIShare,FescueFungiShare/hydroshare,FescueFungiShare/hydroshare,FescueFungiShare/hydroshare,hydroshare/hydroshare,ResearchSoftwareInstitute/MyHPOM,RENCI/xDCIShare,ResearchSoftwareInstitute/MyHPOM