feat(controller/api): Add support for app specific SSL certs

Adds models and views for app specific certs to controller API.
feat(router): Add support for app specific SSL certs

Adds confd and shell code to pull app certificates from etcd,
changes nginx.conf template to add appropriate lines to
server directives for services that have certificates defined
feat(client): Add support for app specific SSL certs

Adds certs:list, certs:add, certs:remove
for the management of app specific certs