NEC plugin: delete old OFC ID mapping tables

NEC plugin: delete old OFC ID mapping tables

Before Grizzly release, data format of OFC ID mapping tables was changed
and there are two types of ID mapping tables for old and new format.
This commit migrate data from old mapping tables into new tables,
drop old mapping tables and remove the logic handling the old tables.

In the db migration scripts, built-in compiler of sqlalchemy does not
support "INSERT INTO table (col1, col2,...) (SELECT ....)" format,
so a custom sqlalchemy.expression compiling method is defined.

Closes-Bug: #1286733
Change-Id: I7dae6b728ab9e10f1dc5d63418a69ee4c26354ea