added interface to manually manage charge of keys

pass/app/PaymentReference.js

pass/lang/de/admin.json

pass/public/js/admin/key-overview.js

pass/public/styles/admin/index.css

pass/public/styles/admin/index.less

pass/public/styles/admin/key-management.css

pass/public/styles/admin/key-management.less

pass/public/styles/admin/key-overview.css

pass/public/styles/admin/key-overview.less

pass/routes/admin/index.js

pass/views/admin/index.ejs

pass/views/admin/key/index.ejs

pass/views/admin/key/overview.ejs