#137 Add check for correct reference parameters

[Rob Bodington]

All ExternalOwlClass and ExternalOwlObject should be Reference Parts in a templates.
Add a check to ensure this

E.g.

Error template.XMI ExternalOwlClass and ExternalOwlObject should be Reference Parts: Template:OASIS:WorkOrder classDateOfIssue [0..1] (Block: Ap239Ap233Psm:ExternalOwlClass)

Error template.XMI ExternalOwlClass and ExternalOwlObject should be Reference Parts: Template:OASIS:WorkOrder classIssuingBody [1] (Block: Ap239Ap233Psm:ExternalOwlClass){/error}