Channel manager REST calls do not work for authors

Channel manager REST calls assume that the backing JCR node is readable by the CMS user. However, authors don't have read access to those node. Hence, their REST calls based on UUIDs fail.

Steps to reproduce:
1. start the page management archetype
2. login as author
3. navigate to the only channel
4. click the 'Pages' button

Expected: the list of pages is shown
Actual: a 'technical error' is shown. The logs contain something like:

[INFO] [talledLocalContainer] 14.03.2014 11:34:02 WARN http-bio-8080-exec-16 [CXFJaxrsHstConfigService.getJaxrsRequest:102] ItemNotFoundException javax.jcr.ItemNotFoundException: 9e3e2008-de13-43e7-a3f0-2b86753e865b
[INFO] [talledLocalContainer] 14.03.2014 11:34:02 WARN http-bio-8080-exec-17 [CXFJaxrsHstConfigService.getJaxrsRequest:102] ItemNotFoundException javax.jcr.ItemNotFoundException: ec88d9f4-5f8f-4d36-b597-2288ad741bfd

These are the UUIDs of the sitemap node and the mount node that the pages dialog uses to do two rest calls (to /pages to get all pages, and to /prototypepages to know whether there are any prototypes defined).