Enable Encryption and/or Signing Only when Annotated [Feature Request]

Currently the library encrypts and signs every field in all entities by _default_ unless `@DoNotEncrypt` or `@DoNotTouch` are applied to fields or types.

The feedback I'd like to provide is that most all projects that I've been a part of aren't willing to accept the overhead of client-side encryption on every field and table. It's usually just a few sensitive fields, where the overhead is justified (or required from a regulatory standpoint). Imagine a project with 50 tables where only one requires client-side encryption. With the current default users need to annotate 49 entities with `@DoNotTouch` and leave one table without any annotations - the one where we do want to encrypt attributes.

This feature request is to add a way to change the default to not do anything unless one of the following new annotations are found on the entity or field: `@Encrypt` or `@EncryptAndSign`.