Bug 18667: Show a diff view of SQL reports when converting

Bug 18667: Show a diff view of SQL reports when converting

This patch reformats the SQL conversion before-and-after view so that it
shows a diff between the two, just as the Manage MARC Import interface
does.

This patch also makes a correction to the JavaScript which is triggered
by the closing of the modal. In Bootstrap 3 "hidden.bs.modal" is the
event name instead of "hidden."

To test, apply the patch and find an SQL report in your reports library
which requires updating.

- Click the "Update SQL" button.
- In the modal window, the "existing" and "updated" SQL should be shown
  side-by-side with colored highlighting of the differece.
- Confirm that the "Update" button still works correctly.
- Also confirm that if you open the preview of another report, the
  "Close" button hides the modal and updates the contents of the modal
  markup. Use your browser's DOM inspector to confirm that <div
  class="modal-body"> contains only <div id="loading"> and its contents.

Revision moves inline style attributes to CSS block.

Signed-off-by: Jesse Maseto <jesse@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>