Add statement preview row to the export

[ddelpiano]

Acceptance criteria:

• create a new row for each connectivity statement exported, which will contain the following
• Predicate will contain composerGenLabel
• Predicate URI will contain http://uri.interlex.org/tgbugs/uris/readable/composerGenLabel
• Predicate Relationship will be "Knowledge Statement"
• Object will be "Knowledge statement"
• Object text will contains the Connectivity statement preview.

[ddelpiano]

@stappan could you please validate the acceptance criteria and the priority? Thanks

[ddelpiano]

@stappan the estimate for this is 6hrs, however since this requires already the predicate URI to be exported as well, we need to work on #373 to be able to satisfy all the acceptance criteria we have in this card, otherwise if we want to postpone #373 the third acceptance criteria we have in this issue will have to be delayed. Thanks