Per editor Connect support v0.1

- Basic plumbing to support connections for a URI rather than global connections. Typical use case is editor requests to connect, but this isn't the only possible use
- Tests pass but need updating to cover new functionality, and re-enable AutoCompleteService test once there is a ServiceDiscovery component that registers and returns services. This is necessary as .Instance won't allow for dependency injection and proper testing.

src/Microsoft.SqlTools.ServiceLayer/LanguageServices/LanguageService.cs

@@ -309,9 +309,9 @@ namespace Microsoft.SqlTools.ServiceLayer.LanguageServices
         /// Callback for when a user connection is done processing 
         /// </summary> 
         /// <param name="sqlConnection"></param> 
-        public async Task OnConnection(DbConnection sqlConnection) 
+        public async Task OnConnection(ConnectionInfo connectionInfo) 
         { 
-            await AutoCompleteService.Instance.UpdateAutoCompleteCache(sqlConnection); 
+            // TODO consider whether this is needed at all - currently AutoComplete service handles its own updating
             await Task.FromResult(true); 
         }