The links.ra file functions similar to the .ra files in 
kent/src/hg/hgGene/hgGeneData directory.  

Currently it is used by the Locus Variants and the ORegAnno tracks.
All the track needs is the accession and the name of the link to build links
to the sources included here.

The fields used to describe an external link are
name	- the key/name for this link
url	- the url with a '%s' if an accession is needed
label	- A label that can be displayed to describe this link
acc	- include this and a yes if the url needs an accession number
needsEncoded	- include this and a yes if the accession should be URL encoded

The fields which are for a link to other UCSC tables
name    - the key/name for this link
label	- a label that can be displayed to describe this link
dataSql	- the sql to retrieve the related data from the table 
	  the caller should have an accession for the query
*the following 2 fields are optional, used when lookup is also a link
dataLink	- This contains the key/name of another entry for an 
		  external link.
dataLinkCol	- This tells you which column in the dataSql query result
		  contains the accesion for the link.


Examples:

name OMIM
url http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=%s
label OMIM
acc yes

name omimTitle2
label OMIM title
dataSql select title, omimId from hgFixed.omimTitle where omimId = '%s'
dataLink OMIM
dataLinkCol 2

