Add support for Emergency Access (#1000)

* Add support for Emergency Access

* Add migration script

* Review comments

* Ensure grantor has premium when inviting new grantees.

* Resolve review comments

* Remove two factor references

src/Core/Enums/EmergencyAccessStatusType.cs

@@ -0,0 +1,11 @@
+namespace Bit.Core.Enums
+{
+    public enum EmergencyAccessStatusType : byte
+    {
+        Invited = 0,
+        Accepted = 1,
+        Confirmed = 2,
+        RecoveryInitiated = 3,
+        RecoveryApproved = 4,
+    }
+}

src/Core/Enums/EmergencyAccessType.cs

@@ -0,0 +1,8 @@
+namespace Bit.Core.Enums
+{
+    public enum EmergencyAccessType : byte
+    {
+        View = 0,
+        Takeover = 1,
+    }
+}