defects 2 & 3 related to bib number based population of new work form
removed commented code
minor code format and comment alterations
DRY work
fix type
don't blank bib populated fields when bib invalidated or blanked, but display message if blanked. Removed call-number field as it is a duplicate of holding number
Merge branch 'master' of github.com:nla/banjo into sc-dsc-279-defects
Merge branch 'sc-dsc-279-defects' of github.com:nla/banjo into sc-dsc-279-defects
Merge pull request #475 from nla/sc-dsc-279-defects

Sc dsc 279 defects, merged.
merged in latest changes.