Fix "nolink" flag

This moves the "link" flag that is automatically added to the beginning
of the flags, this means that "nolink" will override it if it should be
specified in the syntax.
Correct the return type of the blog render function, new version

This lets the blog syntax return false if nothing has been rendered.
This is used by other plugins like the text plugin in order to decide if
the plugin already handles the output mode or if it needs to apply a
custom workaround.