Removed breadcrumb GLOBAL, initiate WPSEO_Breadcrumbs when yoast_breadcrumb is called

Fixes #631
Allow more HTML in breadcrumbs, fixes #636
(and do a stripslashes in `textinput` to prevent slashes from being shown.
Use `wpautop` instead of wrapping in `<p>` tags, fixes #694
Added short code
Only return data in yoast_breadcrumb when display is true
Added scope to WPSEO_Breadcrumbs class methods
Deprecated breadcrumb_output method of WPSEO_Breadcrumbs, use yoast_breadcrumb instead.
Merge branch 'release/1.5' of github.com:Yoast/wordpress-seo into release/1.5
Merge branch 'pr/644' into release/1.5

Conflicts:
	admin/class-metabox.php
	readme.txt
Add `og:updated_time` on single pages
Switch object type of archive pages to `object` instead of `website`
Add inline links to documentation
Use `wp_kses_post` instead of `wp_filter_post_kses` to forego the need for a stripslashes
Soft deprecate the category base removal functionality, relates to #710
Helps if I remove the negative I had for testing ;)
added license submodule + license admin page
pointed submodule to license manager v1
Keyword density: added word boundary check
Add a filter that allows plugin authors to change the URL. Might be used to make relative URLs absolute again. Fixes #717
x-robots-tag noindex the robots.txt file, if it's not static. Fixes #719.
Fix weird looking inline documentation
If we're going to echo based on `$display`, we should always pass false to the `breadcrumb` function as otherwise we output a number 1 later on.