modal focus issues (with patch)

[sswam]

jqModal.js_focus.diff.txt
I am putting these two issues together because my patch covers both.
I imagine you might want to rework it.

1. focusFunc does not run at the right time for an ajax modal, should run after content is loaded.
2. When pressing tab and shift-tab, focus does not stay strictly within the modal.

minor issue: The code is indented with a mixture of tabs (width 2) and spaces.

[sswam]

It's not perfect yet, there are potential issues with other tabbable and non-tabbable fields (<a> tag, tabindex=-1, etc.). It seems there are jQuery selectors :tabbable and :focusable which might help. https://api.jqueryui.com/tabbable-selector/