Secure fee module permissions

It looks I might have a project to use this as a module to collect payment information, but the payment itself would not be handled by this module. Looks like it is reasonable for this task, so I'd disable the fee payment nagging and screens themselves. I found out however, that although there is a permission for that, it is not used for the nagging and the fee screen either. Also, fee admin screens use the general site admin permission and looks like the fee payment list is public (with usernames and dates) which is probably not desired.

So attached patch:

- makes use of the administer fees permission to only provide these users admin permissions on fees
- makes use of the 'pay fee' permission to only nag users if they have this permission and also to only have access to the fee page
- adds a new view fees permission to protect the fee listing page