Restrict creation of new accreditations using a new registered ACCREDITATION_CREATE permission

[Richard Lyders]

I've updated the attached Accreditation.py as follows:

1. implement IPermissionRequestor and register new trac permission: ACCREDITATION_CREATE
2. ensure that only users granted ACCREDITATION_CREATE can create approvals via the /accreditation/new request path
3. only show the create-approval form for users granted ACCREDITATION_CREATE
4. ensure that only the specific author assigned to an approval record can change the approval via the /accreditation/comment request path.

[Richard Lyders]

Registered new ACCREDITATION_CREATE permission to control who can create new accreditation records

[Richard Lyders]

PS: In our environment, anonymous users have access to read-only, but the lack of permissions checking on the creation of accreditations meant that anonymous users could create accreditation records. This enhancement solves that problem by leveraging a new permission ACCREDITATION_CREATE to control who can create new accreditation records.

[Richard Lyders]

This enhancement can be closed as a duplicate of enhancement #13289 considering I've attached a complete unified patch to #13289 with this and all other changes I've implemented.

Complete patch attached with all changes to date ... (the attachment description erroneously calls it a "complete path".

Thanks again for this plugin. We are getting some good use out of it.