2->3 conversion needs to address Location sequences

[jakebeal]

The SBOL 2->3 section doesn't talk about how to assign hasSequence values for the Locations in a Component when converting from SBOL 2 to SBOL 3.

I believe that it should be:

• If there is precisely one sequence in the SBOL2 object, conversion can automatically assign
• Otherwise, conversion cannot assign a sequence, and the produced object will be invalid.

[jakebeal]

Fixed by #467