Initial d7 cleanup of Follow module, refactoring options and block content.

- Moving alignment and icon style form elements to the block configure form.
- Allowing alignment and icon style on the user follow links block as well.
- Renaming alignment and icon style variables to allow for the above.
- Removing css additions from hook_init, and using #attached in a
  renderable array in the block content.
- Allowing custom user styles.
- Moving CSS to a theme template to allow for dynamic icon styles.
- Moved all API and helper functions to a separate file.
- General D7 cleanup.