fixed minor issue with hassubject printout. Minor issue to populate_library_tables (removed unused mainAuthor column)
added comments on tested new functions (show author, subject, book copy)
Merge branch 'master' of https://github.com/g2-aj/cs304 into branch_kris
tested and tweaked insertBookCopy
Merge branch 'master' of https://github.com/g2-aj/cs304 into branch_kris
Merge pull request #28 from g2-aj/branch_kris

Tweaked populate tables sql script, added and tested show functions in Book.Java