rename sps_sequence to iic_sequence in opdb

fps command are now (almost) available through iic and follow the same logic(resources allocation, same opdb table...etc) as the sps ones.
But the opdb sequencing table are still "sps-oriented".
I see two problems :

• renaming sps_sequence -> iic_sequence
• changing some external constraints in visit_set table, which currently only expect sps_visit

class visit_set(Base):
    __tablename__ = 'visit_set'

    pfs_visit_id = Column(Integer, ForeignKey('sps_visit.pfs_visit_id'), primary_key=True, unique=True, autoincrement=False)