preprocessor for domline attributes

With this hook a plugin can add attributes to the preHtml BEFORE a list is drawn..  Before it could only be done after..

For example attempting to use preHtml of ``<span>`` to

```
<ul><li>foo</li></ul>
```
would result in 

```
<ul><li><span>foo</span></li></ul>
```
When what you would want is 
```
<span><ul><li>foo</li></ul></span
```

Needs docs. etc.  Also I suggest a "Post" hook is added too..  This is needed for the ep_align plugin but I'm sure it will affect others too..