Re-architect alias transformations

Brainstorming...

Instead of having so many options for altering aliases (lowercase, separator, strings to remove, punctuation, etc.), what if we re-thought each of these things as an 'alteration', much like ImageAPI has 'transformations' that can be applied to an image. And think of each Pathauto pattern as an 'Image style'. For Pathauto, we'd start out with a few different types of transformations:

1. Change case
2. Find/replace words/strings
3. Find/replace character types

By default we'd have the following transformations enabled as well:
Change case (lowercase)
Find/replace words (a/an/as/at/etc => '')
Find/replace character types (spaces + punctuation => '-')
Trim length
Trim component length

Like Image API in core, there are default settings/transformations, and each pattern could override the settings to add or remove specific transformations. And users can re-order the weight of transformations as well.

Other modules (like Transliteration) could provide their own alias transformations and make them available to Pathauto via a hook.

A lot of this would probably happen on 7.x-2.x development. Just want to get feedback for now.