Removes the 'Child Container' idea (that was bad and would consume lots of mem) and instead we use Scopes. Ensures that the app event handlers are creating during a single Scope operation in the CoreBootManager. Changes MigrationBase and all sub-classes to have an IMigrationContext as a ctor param. Updates the MigrationResolver to resolve Migration instances with the passed in IMigrationContext value. Simplifies MigrationBase since now we know we have a context to work with, there's no need to GetUp/GetDown Expression methods. Updates the MigrationRunner to use the MigrationContext instead of creating one itself.

src/Umbraco.Core/Models/Mapping/ModelMapperConfiguration.cs

@@ -4,10 +4,7 @@ namespace Umbraco.Core.Models.Mapping
 {
     /// <summary>
     /// Used to declare a mapper configuration
-    /// </summary>
-    /// <remarks>
-    /// Use this class if your mapper configuration isn't also explicitly an ApplicationEventHandler.
-    /// </remarks>
+    /// </summary>    
     public abstract class ModelMapperConfiguration
     {
         public abstract void ConfigureMappings(IMapperConfiguration config, ApplicationContext applicationContext);