Changes the CoreBootManager to resolve migrations through the use of the PluginManager instead of having the migration types hardcoded.

src/Umbraco.Core/PluginManager.cs

@@ -11,6 +11,7 @@ using System.Xml.Linq;
 using Umbraco.Core.IO;
 using Umbraco.Core.Logging;
 using Umbraco.Core.Models;
+using Umbraco.Core.Persistence.Migrations;
 using Umbraco.Core.PropertyEditors;
 using umbraco.interfaces;
 using File = System.IO.File;
@@ -458,6 +459,15 @@ namespace Umbraco.Core
             return ResolveTypes<IMacroPropertyType>();
         }
 
+        /// <summary>
+        /// Returns all available IMigrations in application
+        /// </summary>
+        /// <returns></returns>
+        internal IEnumerable<Type> ResolveMigrationTypes()
+        {
+            return ResolveTypes<IMigration>();
+        }
+
         /// <summary>
         /// Gets/sets which assemblies to scan when type finding, generally used for unit testing, if not explicitly set
         /// this will search all assemblies known to have plugins and exclude ones known to not have them.