Taxonomy reconfigured

Reconfigured `taxonomy` Class to take advantage of code from other field
classes.  Also rewrote `select-advanced` normalize function, according
to an article from Kaiser:
https://crappycode.wordpress.com/2012/12/27/defaults-of-defaults/
Select-advanced regressed
Added before and after save actions

I ran into a situation where I needed this.  Basically, I wanted a way
to update the post via `wp_insert_post` after all the meta data was
saved because I wanted to use said meta data to do so.  I took the
proper precautions to prevent infinite loops with the `save_post` action
by disabling it before the `do_action` calls and reinstating it after.
Merge pull request #191 from funkedgeek/master

Taxonomy reconfigured