Standardize interface for all CRUD APIs accessible via Contacts instance

[vestrel00]

While working on #147 in preparation for #144 and #145, I realized that having an interface that all Create (Insert), Read (Query), Update, and Delete (C.R.U.D.) implements will give us some structure to follow and help a lot. It has the following benefits;

1. It gives a sense of uniformity for consumers as well as maintainers.
2. It allows maintainers to easily add functions that all APIs must implement.
3. It allows internal hooks to every API's lifecycle.

The contract should be as loose as possible to give the most amount of flexibility. Only bare essential functions should be added.

[vestrel00]

My initial thoughts on what this should look like,

package contacts.core

interface CrudApi : Redactable {

    interface Result : Redactable
}

[vestrel00]

Included in release; https://github.com/vestrel00/contacts-android/releases/tag/0.1.10