Remove a bunch of redundancy in variables and header text styles

These changes are to  simplify bitters and are opinionated based on building web applications and not web sites.

* Remove header styles because they always get changed. The initial styles just add overhead to be changed. 
* Remove `blockquote` and `cite` styles. I've hardly ever used them and changed them when I have.
* Create `$base-spacing-small` for all the places where we were using `$base-spacing / 2`
* Remove unnecessary duplication in form variables.
* Remove unnecessary duplication in link and button variables.
* Remove `$base-background-color` as it rarely is used more than once.

For me: 
* The defaults aren't good and I don't know what ones would be. I've changed them every time I use them. 
* I end up putting most of my header styles in a class so that the styles are independent of the level of the header. 
* I rarely find myself needing these more than once. I feel that until I've used the size more than once it doesn't need to be in a variable.