N°3526 - Clean up pass on UIBlocks

- Move UIBlock::ENUM_BLOCK_FILES_TYPE_XXX to iUIBlock
- Add PHPDoc
- Remove Object return type hint on overloadable methods
- Add scalar return type hint
- Add type hint on parameters

sources/application/UI/Base/Component/PopoverMenu/PopoverMenuItem/PopoverMenuItem.php

@@ -55,7 +55,7 @@ class PopoverMenuItem extends UIBlock
 	/**
 	 * @inheritDoc
 	 */
-	protected function GenerateId()
+	protected function GenerateId(): string
 	{
 		return parent::GenerateId().'--'.utils::GetSafeId($this->oPopupMenuItem->GetUID());
 	}