Added description of the relaxed transactional semantics in InMem DB.
Removed obsolete (tags will be immutable soon) tag manipulation and templating utils.
Transformed tag mutators towards immutable chain builders.
Removed unused tag util.
Fixed tag proxy mutators (turned into immutable tag chain builders).
Fixed tag copy mechanism (not all fields were copied).
Adjusted widget and tag utils to the new "immutable" design.
Improved AJAX error message.