old linking pattern referenced in MR spec

[mattgarrish]

Our original idea for adding link elements to the container was that they would follow the rootfiles element, but during the 3.0.1 revision the AHL proposal was changed to add a links element wrapper.

Romain has noted that the prose in section 4.4.4 wasn't updated to reflect this new reality:

The location of the Rendition Mapping Document is identified in the Container Document using an [OCF301] link element child of the root container element, where:[1]

We should either remove mention of it being a child of the container or switch "root container element" to "links element".

I'll add this to the errata for the document. We can perhaps address this oversight when we look at consolidation during 3.1.

[1] http://www.idpf.org/epub/renditions/multiple/#sec-4.4.4

/cc @mgylling @murata0204 @rdeltour