Separate common interfaces from client-specific classes

Changes:
- Move client-specific classes to client/src/models
- Extract common interface to standalone files in common/interfaces
- Remove unused features from client-specific classes
    - These are features which were once used on the old server, but are now no longer needed
    - Remove getObject() method for Account, Contact, and Conversation
    - Remove lookups, registrationState and registeringName from Account
    - Remove resolving logic from Contact
    - Remove requests and listeners from Conversation (once used for Socket.IO and promises on server)
- Rename services/Conversation.ts to services/conversationQueries.ts
- Update imports

Future work:
- Create interface versions of Account, Contact, and Conversation
- Create new interfaces to replace Records on server

GitLab: #94
Change-Id: Ia51fe6ebeda44a30887d851a5564569dc290e5ed
diff --git a/common/src/index.ts b/common/src/index.ts
index 9c36a37..1d3c7f6 100644
--- a/common/src/index.ts
+++ b/common/src/index.ts
@@ -15,12 +15,10 @@
  * License along with this program.  If not, see
  * <https://www.gnu.org/licenses/>.
  */
-export * from './Account.js';
-export * from './AccountDetails.js';
-export * from './Contact.js';
-export * from './Conversation.js';
 export * from './enums/http-status-code.js';
+export * from './enums/registration-state.js';
 export * from './enums/websocket-message-type.js';
+export * from './interfaces/account-details.js';
+export * from './interfaces/message.js';
 export * from './interfaces/websocket-interfaces.js';
 export * from './interfaces/websocket-message.js';
-export * from './util.js';