Completely remove HTML sitemap functionality, fixes #1549
Remove test class for sitemap walker
Change unit test to use other setting to test whether default settings aren't saved.
Merge branch 'master' into remove-html-sitemap

Conflicts:
	admin/class-metabox.php
	inc/class-wpseo-meta.php
fix array
Merge pull request #1552 from Yoast/remove-html-sitemap

Completely remove HTML sitemap functionality, fixes #1549