Move the permission and role constants from JcrSession to separate public interfaces

There are several constants for roles and permission actions in JcrSession. These have an incorrect case (e.g., "ModeShape" rather than "MODESHAPE"), and their use by clients requires importing the JcrSession class.

The old constants are likely not used by clients (as they were undocumented), and so we can remove them altogether (rather than merely deprecate them).