Add disable send policy (#1130)

* Add Disable Send policy

* Test DisableSend policy

* PR Review

* Update tests for using CurrentContext

This required making an interface for CurrentContext and mocking out
the members used. The interface can be expanded as needed for tests.

I moved CurrentContext to a folder, which changes the namespace
and causes a lot of file touches, but most are just adding a reference

* Fix failing test

* Update exemption to include all exempt users

* Move all CurrentContext usages to ICurrentContext

* PR review. Match messaging with Web

src/Core/Services/Implementations/UserService.cs

@@ -14,6 +14,7 @@ using Bit.Core.Models.Business;
 using U2fLib = U2F.Core.Crypto.U2F;
 using U2F.Core.Models;
 using U2F.Core.Utils;
+using Bit.Core.Context;
 using Bit.Core.Exceptions;
 using Bit.Core.Utilities;
 using System.IO;
@@ -46,7 +47,7 @@ namespace Bit.Core.Services
         private readonly IPolicyRepository _policyRepository;
         private readonly IDataProtector _organizationServiceDataProtector;
         private readonly IReferenceEventService _referenceEventService;
-        private readonly CurrentContext _currentContext;
+        private readonly ICurrentContext _currentContext;
         private readonly GlobalSettings _globalSettings;
         private readonly IOrganizationService _organizationService;
 
@@ -74,7 +75,7 @@ namespace Bit.Core.Services
             IPaymentService paymentService,
             IPolicyRepository policyRepository,
             IReferenceEventService referenceEventService,
-            CurrentContext currentContext,
+            ICurrentContext currentContext,
             GlobalSettings globalSettings,
             IOrganizationService organizationService)
             : base(