Split LibraryScan and Rematching into separate background tasks (#166)

* Simplified LibraryScan service and moved rematching to it's own service

* Added rematcher to tasks blocked by OrganiseLibrary

gaseous-tools/Database/MySQL/gaseous-1004.sql

@@ -36,4 +36,7 @@ CREATE TABLE `Relation_Game_Themes` (
   `ThemesId` BIGINT NOT NULL,
   PRIMARY KEY (`GameId`, `ThemesId`),
   INDEX `idx_PrimaryColumn` (`GameId` ASC) VISIBLE
-);
+);
+
+ALTER TABLE `Games_Roms` 
+ADD COLUMN `LastMatchAttemptDate` DATETIME NULL AFTER `LibraryId`;