[Matrix]: allow to write multiple contig portions to EM dense mat.
[Matrix]: allow to write multiple contig portions to EM dense mat.

icoming/FlashX,flashxio/FlashX,icoming/FlashX,icoming/FlashGraph,icoming/FlashGraph,flashxio/FlashX,zheng-da/FlashX,flashxio/FlashX,icoming/FlashX,icoming/FlashGraph,icoming/FlashGraph,zheng-da/FlashX,zheng-da/FlashX,flashxio/FlashX,icoming/FlashGraph,icoming/FlashX,icoming/FlashX,flashxio/FlashX,zheng-da/FlashX,flashxio/FlashX,zheng-da/FlashX