Added 'serialize(conservedRegion)' to cellbase serializers; conservedRegionParser now extends CellbaseParser; Some cleaning in CellbaseMain
Refactorized GeneParser: now extends CellbaseParser and just has one 'parse' method; Fixed genomeSequence parser creation in CellbaseMain; Change in CellbaseParser: removed 'serialize' method, now parsers call directly to 'serialize' methods from CellBaseSerializer