[7.1] Missing note about expected configuration of attribute of singleton policy in Development Guide

Book: Development Guide
Revision: n_2306931_development-guide_version_7.0_edition_1.0_release_0-revision_9024531
Issue description: In section 7.5., under the title "Creating a Singleton Deployment" there are two examples of adding new singleton policy through CLI batch. If user/customer follows these examples and he uses custom cache container, then it will probably end up by an error message if the cache container is not configured in expected way. This is caused by fact, that the policy depends on default-cache attribute of given cache-container and if it is not defined, adding of policy is not successful.
Suggestion for improvement: There should be note, that the used cache container must have defined its default-cache attribute.