Switch to using JPA to handle relationships between WeblogTemplates and CustomTemplateRenditions.

git-svn-id: https://svn.apache.org/repos/asf/roller/trunk@1616650 13f79535-47bb-0310-9956-ffa450edef68
Removed temporary WeblogTemplate accessors from TemplateRendition, as it's not relevant for implementing class SharedThemeTemplateRendition.

git-svn-id: https://svn.apache.org/repos/asf/roller/trunk@1616651 13f79535-47bb-0310-9956-ffa450edef68