Add an interface for custom list items.
Implement CustomListItem for built-in and custom lists.

First implementation of built-in custom list

Generalize custom list interface in order to provide for facility to manage
system's built-in list like ticket statuses, priorities ...etc.

pjax:complete is only called after an AJAX page load. If a user navigates
forward or backward and the page loads from local cache, then pjax:complete
is not fired. pjax:end, however, is always fired.

Add original and last message quotes to canned responses

Otherwise, no column will be added to the %ticket__cdata table and the
ticket queue pages will be crashed (empty).

The default mode going forward will be to insert when Rich Text support is
enabled and append otherwise. To clear the draft the user can simply click
reset or delete draft icon on the bar.

Enable delete draft option on reply & internal note boxes for consistency.

If the advanced search dialog is up, avoid refreshing the page

htmLawed stripped/discarded <div> tags nested inside inline tags such as
<a>. The previous replacement engine would replace <img> tags with <div>
tags and would cause the HTML to be corrupted by htmLawed.

This patch uses <span> tags which have CSS rules to be displayed as
inline-blocks. This should stay truer to the normal sizing and placement of
the original <img> tag.

And use admin-defined site logo

This reverts commit b6b2b857.

The user should not have to step over it