Support for adding <math> or <svg> elements in inline contexts whenever possible

I've added support for employing `<math>` or `<svg>` elements in inline contexts whenever possible. 

The only exceptions are situations where doing so would result in the Schema being nondeterminist. This is relevant for the small subset of elements that can accept block or inline children (like a `<li>`). In these situations, you have to choose whether to have block children or inline children, e.g. this:

````html
<li>Bullet #1</li>
````

or:

````html
<li><p>Bullet #1</p><p>Bullet #2</p>
````

Because `<math>` and `<svg>` can be used in both block and inline contexts, they have to be classified by default into one group or the other for use in contexts like the above. So, I've classified them by default as block elements, which seems more appropriate.