Edit profile type

From the admin/structure/profiles page, you can either edit an existing profile type or add a new one. Current code doesn't do anything yet. Here's my first attempt at moving this forward, or at least generate some discussion.

This form is very similar to the one for content types except for, among others, the following:

1. the current code doesn't have a "description" field in the profile_type table.
2. it doesn't address cases where one might want to change the type name (content type allows for this and keeps track of it in the "orig_type" column of the node_type table.
3. no additional_settings yet - I believe these will probably be stored in the "data" column, as a serialized array.