Support FTS and bulk loading indices

[nicoloesch]

Changes in this commit

• Create FTS indices
• Support other SQLAlchemy indices
• Support bulk loading of indices after table creation.

Rationale
The changes include optimisations to support a wide variety of indices. Particularly, the indices can be set in the SQL ORM table, but the respective staging table will not include them as they are computed.
This has several advantages:

1. Loading the tables from .csv doesn't cause warnings as the newly created index column isn't populated
2. Computing the indices after bulk ingestion has the advantage that each index is not computed per row that is ingested. This results in a detrimental increase in performance, particularly for FTS indices.

[gkennos]

reviewed