new file:   plugins/server.admin/app/admin/img/providers/vk-config.png
add yandex provider
docs: http://api.yandex.ru/oauth/doc
	new file:   plugins/server.admin/app/admin/img/providers/yandex-config.png
	new file:   plugins/server.admin/app/admin/img/providers/yandex-keys.png
	new file:   plugins/server.admin/app/admin/img/providers/yandex.png
	new file:   providers/yandex.json
	new file:   providers/yandex.png
	deleted:    plugins/server.admin/app/admin/img/providers/yandex.png
Merge pull request #26 from valmat/yandexprov

Add Yandex OAuth 2.0 provider