Tags decorator should be more configurable

[nponiros]

Currently it supports only a page called tags.html. The string "tags" in the URL of a tag is currently fixed and can not be changed. It should be changed to allow the user to define the URL for the page which shows all tags. This will probably be done by defining a template in the createTagsFor configuration.

This limitation also means that if the user wants to tag more than one different contents, the tags for all contents will only be in one page. There is no way to define one page for each tagged content.