Clarify imported attributes

Goal is to improve import of attributes. With 0.10.0 some issues:

we copy Requirement.ChapterName into LongName, whereas we don't do it on Module
ReqIf.Prefix is not imported on Module, but there is on Requirement
Some attribute can't be imported even if the user has put them into preferences. (ForeignCreatedBy, ForeignCreatedOn, ForeignDeleted, etc)

As there is LongName, Name, ChapterName, Text, and it differ according to tools exporting to ReqIf, we will not try to merge them into one, but import all of these fields if present.

ReqIF.LongName is imported to ReqifLongName ReqIF.Name is imported to ReqifName ReqIF.ChapterName is imported to ReqifChapterName ReqIF.Text is imported to ReqifText

ECLIPSE-555394 POLARSYS-2503 @pdu 2019-06-10

cp-api / capella-requirements-vp

Clarify imported attributes #69