added xref records relevant to vectorbase array mappings (anopheles / aedes)

new methods for creating the display xref and gene descriptions by reading the core database and not just using the mapping files. This means it will be possible to add sources one at a time without trashing the display_xrefs and gene descriptions. This was previously a problem as if you are just adding a new source then only that source could be used for getting the descriptions etc.

Added ability to project gene descriptions as well as names etc. Projected descriptions are currently stored the 'old' way, i.e. in the actual gene description field rather than in the info_* fields in the xref table.