create fec_fitem_sched_a/b_2019_2020 partition tables and related objects

[fecjjeng]

With new cycle 2019_2020, partition for tables disclosure.fec_fitem_sched_a/b for the new cyclde (disclosure.fec_fitem_sched_a/b_2019_2020). The tables were already created as part of the Java transfer process when it first encountered the incoming data for cycle 2019/2020 so we will not miss any incoming data. However, official migration script is need to add these to the version controlled base of the database structure.

• create migration script to "officially" add these new partition tables disclosure.fec_fitem_sched_a/b_2019_2020
• update index creation functions for these two tables to simplify the index creation when new child partition tables are created.

[hcaofec]

close this ticket since PR is merged.