[ConeSearch] Eurovo grade is C

[mmebsout]

To improve this grade to A++ there is only one thing to fix :

http://www.ivoa.net/documents/REC/DAL/ConeSearch-20080222.html

"In the case of error, the service MUST respond with a VOTable that
contains a single PARAM element or a single INFO element with
name="Error", where the corresponding value attribute should contain
some explanation of the nature of the error...."

So far there is the possibility of having several Info tags for errors with name = "QUERY_STATUS" or name = "Error in <attributekey>"

I suggest this change in src/fr/cnes/sitools/astro/vo/conesearch/ConeSearchInputParameters.java Line 148