Bug 16437 - Automatic item modifications by age needs prettying

Bug 16437 - Automatic item modifications by age needs prettying

This patch makes layout and behavior changes to the automatic item
modifications by age interface, bringing some aspects of it closer into
conformance with established interface patterns.

- The intial view is now a standard table of information about existing
  rules, or a message dialog saying there are no rules.
- If there are no rules, a toolbar button reads "Add rules."
- If there are existing rules, the toolbar button reads "Edit rules."
  - Clicking the button leads to the rules edit interface, which now has
    a floating toolbar with "Add rule," "Save," and "Cancel" buttons.
  - Clicking the "Add rule" button displays a blank rule block.
    - If you are adding a rule to existing rules, the new block is
      appended at the bottom, and the page scrolls to the new rule.
    - As you add or remove rule blocks, the legend containing the rule
      count updates so that the numbers are sequential.
    - In each rule block, "age" and "substitutions" are now required.
      The age field is now validated to require a number.
    - The add/remove condition/substitution links now have more
      descriptive text labels.
    - The control to remove a rule is now a link in the <legend> element
      associated with each rule.
- Most JavaScript for this page is now in a separate file.
- Breadcrumbs are updated to be a little more specific.

To test, apply the patch and clear your browser cache if necessary.

- Go to Tools -> Automatic item modifications by age.
- Test adding and removing rules.
- Test removing all rules.
- Test adding and removing conditions and substitutions within rules.
- Test submitting the form without filling in required fields.

Followed test plan, works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>