add option Brand use_middlewarePing

iOSClient/Brand/NCBrand.swift

@@ -88,6 +88,7 @@ class NCBrandOptions: NSObject {
     public let use_themingColor:                Bool = true
     public let use_themingBackground:           Bool = true
     public let use_multiDomains:                Bool = false
+    public let use_middlewarePing:              Bool = false
     
     public let disable_intro:                   Bool = false
     public let disable_request_login_url:       Bool = false