WebStat: additional stats and various improvements

• Plugged additional statistics:
  1. Comments frequency
  2. Number of loans
  3. Web submissions
  4. Loan statistics
  5. Loan lists
  6. Renewals lists
  7. Number of overdue returns
  8. Percentage of overdue returns
  9. ILL Requests statistics
  10. ILL Requests list
  11. Percentage of satisfied ILL requests
  12. Items statistics
  13. Items list
  14. Hold requests statistics
  15. Hold requests lists
  16. User statistics
  17. User lists
  18. journals
  19. loanrequest
  20. BibCirculation yearly/monthly reports

• Support for JQuery Flot graphs, table/list views, and Excel export

• Additional improvements and bug fixes