Add reset form API function

Author: spinn

src/components/FlowForm.vue

@@ -777,6 +777,11 @@
 
       setDisabled(state) {
         this.disabled = state
+      },
+
+      reset() {
+        this.questionModels.forEach(question => question.resetAnswer())
+        this.goToQuestion(0)
       }
     },
 

src/models/QuestionModel.js

@@ -176,6 +176,8 @@ export default class QuestionModel {
         if (this.answer === optionValue || (isArray && this.answer.indexOf(optionValue) !== -1)) {
           o.selected = true
           ++numSelected
+        } else {
+          o.selected = false
         }
       })
 
@@ -197,6 +199,14 @@ export default class QuestionModel {
     }
   }
 
+  resetAnswer() {
+    this.answered = false
+    this.answer = this.multiple ? [] : null
+    this.other = null
+
+    this.resetOptions()
+  }
+
   isMultipleChoiceType() {
     return [QuestionType.MultipleChoice, QuestionType.MultiplePictureChoice].includes(this.type)
   }