Merge branch 'master' into branch_lin
Add class librarian
Merge branch 'master' into branch_lin
Merge pull request #13 from g2-aj/branch_alshahna

process return transaction ... in progress
Merge pull request #14 from g2-aj/branch_alshahna

completed process return transaction in clerk.java -- still needs to be ...
Merge pull request #15 from g2-aj/branch_alshahna

added DateHelper class to calculate Date class, and updated the processR...
Finished check book exist function
Merge branch 'master' into branch_lin
Added not null constraints to tables in lib_tables
Merge pull request #16 from g2-aj/g3-ks

Added not null constraints to tables in lib_tables
Merge pull request #17 from g2-aj/branch_alshahna

completed checksOverdue items clerk transaction, and fixed Borrower to c...
Finished first half of generate report function
Merge pull request #18 from g2-aj/branch_lin

Branch lin
Created new class for borrower transactions. Renamed borrower table class to BorrowerAndType.
Merge branch 'master' of https://github.com/g2-aj/cs304 into g3-ks
Merge pull request #19 from g2-aj/g3-ks

G3 ks
fixed checkout items in finding an available copy, and added dearch by keyword functions in Borrower.java