[1.7.x] Made sqlite's remove_field behave like the base backend.

Backport of 61d783f3d7c9d4c7a0ac05f7fbbaba78e5cef5aa from master.
[1.7.x] Fixed remove_field for spatialite schema changes.

Backport of f915d39afe3565ac2355de57c11843530b96f3bc from master.