Biography cleanup

#56 - Biography updates to user platform (and link to the new biography page from people pages)
#60 - Forgot password and better sign in links for the user platform
Again, this can be abstracted into a method defined on `Contribution` but overridden on `Biography`. Since `image` comes from a decorator, you could define a new `BiographyDecorator` that inherits from `ContributionDecorator`, mirroring the inheritance pattern in `app/models`.