A Context at this point is still:
- a way to specify ''what'' Trac resource is being accessed. This is the ''resource descriptor'' side, the ''input'' details.
- a way to specify ''how'' that Trac resource is being accessed. This is the ''rendering context'' side, the ''output'' details.
This also brings in some changes done in the [PermissionPolicy security] branch, focusing for this changeset on the r4666 fixes.