Issue #1325116 by xenophyle, xjm: Clean up API docs for Aggregator module.

core/modules/aggregator/aggregator-feed-source.tpl.php

core/modules/aggregator/aggregator-item.tpl.php

core/modules/aggregator/aggregator-summary-item.tpl.php

core/modules/aggregator/aggregator-summary-items.tpl.php

core/modules/aggregator/aggregator-wrapper.tpl.php

core/modules/aggregator/aggregator.admin.inc

core/modules/aggregator/aggregator.api.php

core/modules/aggregator/aggregator.module

core/modules/aggregator/aggregator.pages.inc

core/modules/aggregator/aggregator.parser.inc

core/modules/aggregator/aggregator.processor.inc