Create new enums to type state strings and numbers on server

New enums:
- RegisteredNameFoundState (for NS lookups which emit a RegisteredNameFound signal)
    - This enum is in common/ since it is used by the common LookupResult interface
- NameRegistrationEndedState (for the NameRegistrationEnded signal)
- RegistrationState (for the RegistrationStateChanged signal)
- MessageState (for the AccountMessageStatusChanged signal)
- ConversationMemberEventType (for the ConversationMemberEvent signal)

Other changes:
- Update jamid.ts and jami-signal-interfaces.ts to use these new enums
- Update routers to use the enum members rather than magic constants

GitLab: #89
Change-Id: Ief38df0d4a35c6ecf96375bba01773e60e07b888
diff --git a/common/src/interfaces/lookup-result.ts b/common/src/interfaces/lookup-result.ts
index 1d18a14..b3c21bd 100644
--- a/common/src/interfaces/lookup-result.ts
+++ b/common/src/interfaces/lookup-result.ts
@@ -16,7 +16,14 @@
  * <https://www.gnu.org/licenses/>.
  */
 export interface LookupResult {
-  state: number; // TODO: Create enum for state
+  state: RegisteredNameFoundState;
   address: string;
   username: string;
 }
+
+export enum RegisteredNameFoundState {
+  Found,
+  InvalidResponse,
+  NotFound,
+  Error,
+}