Change admin_add/admin_edit to use saveAll

Related to issue comment: https://github.com/croogo/croogo/issues/514#issuecomment-53711274

This change allows a user to extend the blocks plugin and save related data in another table.  Handy if you want your blocks to have site specific fields so they can become a lot more flexible.

I will release a plugin that demonstrates this soon.
Add better support to create input addons

- Options can accept either 'append' or 'prepend' setting
- Markup for addons are passed through the 'addon' setting
Don't apply formInput for checkbox wrappers when multiple => checkbox
Remove unnecessary class option
Use 'append' option when creating addons