Show warning if select_multiple value has spaces

@theywa, it may be interesting and useful to follow the procedure of getting the feature you added in Enketo Core, activated in Enketo Express. In this case, I expect it to be straightforward, but it will be good to test and this way you can also see how translation strings get added to Enketo Express and how the modal dialog works (automagically).

• update enketo-core package.json (the commit that added the feature or the latest enketo-core commit)
• npm install and then run with grunt develop
• update changelog of enketo-express (just copy entry from enketo-core)
• do final test with actual forms. There are two methods I use:

1. Upload a form to e.g. KoBoCAT and then manually make an API call to your local enketo-express installation with that form, using the POST /survey api call. After that you can open your form in the browser using the returned URL.
2. Upload a form anywhere on a webserver and use the http://localhost:8005/preview?form=http://theurl/to/form.xml

• You should be seeing the nice modal dialogs instead of window.alert.
• While running grunt develop the new translation key should have been automatically detected and added to /locales/src/en/translation.json. You have to copy the English string that you used in fake-translator.js in enketo-core). Once the commit is pushed to master, the translators will be automatically alerted that there is a new string to be translated (in Transifex).

[theywa]

@MartijnR - I create PR in enketo-core

[theywa]

@MartijnR, I found an issue when testing. The modal dialog only showed the last alert message like this when it supposedly showed 3 alerts. My guess this happens because of the modal dialog worked differently than the alert window. Alert window will pause the load process until the user closes it and the modal dialog will be fired after the process is done so the message got override with the new one. I think maybe we can save all the message on an array then call the dialog.alert at the end of the loop with all the array of message joined with break line, like

if ( multiple && ( value.indexOf( ' ' ) > -1 ) ) {
      alerts[alerts.length] = t( 'alert.valuehasspaces.multiple', { value: value } );
} 
...
if ( alerts.length > 0 ) {
      dialog.alert( alerts.join("<br>") );
}

and the modal dialog will look like or we can just join the value in 1 message like