[ios] re-add support for formats option
[ios] re-add support for formats option

fixes #426

Keyoniq/phonegap-plugin-barcodescanner,sovanta/phonegap-plugin-barcodescanner-custom-ui,Keyoniq/phonegap-plugin-barcodescanner,Keyoniq/phonegap-plugin-barcodescanner,sovanta/phonegap-plugin-barcodescanner-custom-ui,sovanta/phonegap-plugin-barcodescanner-custom-ui,sovanta/phonegap-plugin-barcodescanner-custom-ui,sovanta/phonegap-plugin-barcodescanner-custom-ui,Keyoniq/phonegap-plugin-barcodescanner,Keyoniq/phonegap-plugin-barcodescanner