Enhancement of how breadcrumbs for Custom Post Types are named.

As suggested in: http://wordpress.org/support/topic/change-custom-post-type-label-for-breadcrumbs
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Enhancement-breadcrumbs-cpt

Conflicts:
	readme.txt
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Enhancement-breadcrumbs-cpt
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Enhancement-breadcrumbs-cpt
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Enhancement-breadcrumbs-cpt
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Enhancement-breadcrumbs-cpt
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Enhancement-breadcrumbs-cpt
Even though it's common to use a PLUGINNAME_URL constant for creating file paths, the use of this breaks the plugins_url filter.

This pull request replaces all uses of the WPSEO_URL constant with the correct usage of plugins_url()
Removed WPSEO_URL definition
Making this change isolated and updated readme
Removed unused WPSEO_FRONT_URL constant
* Applied a number of settings form best practices - props [Jrf](http://profiles.wordpress.org/jrf).

* Improved form support for UTF-8 - props [Jrf](http://profiles.wordpress.org/jrf).
* Corrected faulty multisite option registration - props [Jrf](http://profiles.wordpress.org/jrf).
Reverted removal of settings errors() until settings are properly validated in the right way
Changed all requires and includes to require_once() and removed slashes at the beginning of the path where needed (both WPSEO_PATH and ABSPATH have a trailing slash)
Stabilized error message include
One more...
Merge pull request #311 from jrfnl/master

* (Temporary) fix for metabox styling for users using the MP6 plugin
* Minor fix in localization loading
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Fix-breaking-of-plugins-url-filter-hook

Conflicts:
	readme.txt
Redo MP6 fix as auto-merge had undone it
Merge pull request #312 from jrfnl/Fix-breaking-of-plugins-url-filter-hook

Fix breaking of plugins url filter hook