new: function C4::Date::get_date_format_string_for_DHTMLcalendar based on

new: function C4::Date::get_date_format_string_for_DHTMLcalendar based on
the system preference prefered date format.

improvement: book fund list and budget list screen redesigned. Filters on
each field. Columns are not sortable yet. Using DHTML Calendar to fill date
fields instead of manual filling. Pagination system. From the book fund
list, you can reach the budget list, filtered on a book fund, or not. A
budget can be added only from book fund list screen.

bug fixed: branchcode was missing in table aqbudget.

bug fixed: when setting a branchcode to a book fund, all associated budgets
move to this branchcode.

modification: when adding/modifying budget/fund, MySQL specific "REPLACE..."
statements replaced by standard SQL compliant statement.

bug fixed: when adding/modifying a budget, if the book fund is associated to
a branch, the branch selection is disabled and set to the book fund branch.