improved checkout.html and initial returns commit

todo: notify holdee(returns), testing
implemented return functionality
update return functionality

retrieves email in qresult and book info in qbook
implementation of checkout and return

checkout only one item at a time
return error coverage

returning a book that was never taken out
fixed book checkout db inconsistensy
implement overdue report
added success messages
overdue report shows more info
removed old overdue file
overdue implementation bugs
fetch origin
fix bug in display
merge?