This API defines a secure import flow, that allows to import data in
a container, then checks the container for data consistency and finally
process data and appended them to GraphAPI and
AttributesAPI.
See org.gephi.io.importer.spi package for defining new
importers and org.gephi.io.processor.spi for processors.
Processors come after importers and are responsible for appending
import results.
Import tasks can also carefully logging what they do and where some problems where found. The report can then be displayed to users.