[BioRDF] Antibodies use case draft

Quick pass:  
http://esw.w3.org/topic/HCLSIG_BioRDF_Subgroup/Tasks/Reagents

BTW, the template has a number of headings that I find difficult to 
distinguish:

Task Objectives
Rationale
Scope
Use case context
Problem statement for this use case

Speak to all tomorrow...

-Alan