Make goose annotations case-insensitive

[mfridman]

There are currently 7 goose annotations that may be found in a .SQL file. These annotations define how goose behaves when it reads a .SQL file (outdated post, but should give you an idea of how/why to use these annotations).

Over the years as different folks worked on the project, we've mixed uppercase and pascal case. For consistency, we should make these (and future) annotations case-insensitive.

While we do this, we should also add validation to ensure if we come across -- +goose [annotation] that the annotation is known to goose and otherwise error.

+goose Up
+goose Down
+goose StatementBegin
+goose StatementEnd
+goose NO
+goose ENVSUB
+goose ENVSUB