Update generic routes for administrative layer

Update the current routes to generic ones:

1. /admin — entry point;
2. /admin/auth — basic authentificator;
3. /admin/session/validate — validate a session;
4. /admin/session/extend — extend a validated session to sess_timeout
5. /admin/session/close — close a session.

Sample config:

{
  "routing": {
    "label": "Routing settings",
    "group": {
      "routes": {
        "login": {
          "label": "Default route",
          "route": {
            "path": "/admin",
            "hdlr": {
              "default": "browse",
              "/api": "browse_api"
            }
          }
        },
        "authentication": {
          "label": "Authenticate a consumer route",
          "route": {
            "path": "/admin/auth",
            "hdlr": {
              "/api": "auth_api"
            }
          }
        },
        "validate": {
          "label": "Validate a session route",
          "route": {
            "path": "/admin/session/validate",
            "hdlr": {
              "/api": "validate_session_api"
            }
          }
        },
        "extend": {
          "label": "Extend a validated session route",
          "route": {
            "path": "/admin/session/extend",
            "hdlr": {
              "/api": "extend_session_api"
            }
          }
        },
        "close": {
          "label": "Close a validated session route",
          "route": {
            "path": "/admin/session/close",
            "hdlr": {
              "/api": "close_session_api"
            }
          }
        }
      }
    }
  }
}