When using 'relation add X blocked-by Y', the API is called with swapped
IDs (Y blocks X), but the success message was showing the API's returned
identifiers (in the swapped order) instead of the user-specified order.
Fixes: the message now uses the original issueIdentifier and
relatedIssueIdentifier variables, so 'relation add ENG-123 blocked-by ENG-456'
correctly shows '✓ Created relation: ENG-123 blocked-by ENG-456'.
Closes#152
Peter Schilling