[C2] Re-enable blogs tool

[ywarnier]

The blogs tool has been disabled (and tables c_role* and c_permission* have been removed for excessive complexity).

First, add the tool back in c_tool_intro (similar to what was done for dropbox).
Second, ensure blog, blog_post, blog_attachment, blog_comment and maybe blog_task have been declared as resources.
Third, convert the tool's queries so it can work under C2.

[christianbeeznest]

It is implemented a version of blog , it requires testing

Thanks