Add method for purging Author Pages

See WebSharks/Quick-Cache#80
Fix auto_purge_author_page_cache() docblocks.
Add new "Auto-Purge Author Page" option to "Clearing the Cache" settings panel
Fix docblocks and use esc_html() on author name in auto_purge_author_page_cache()
Merge branch 'f-quick-cache-80' into 000000-dev