fix(picker): selectionIndex always initialized

Author: manucorporat

src/components/datetime/datetime.ts

@@ -563,6 +563,7 @@ export class DateTime extends Ion implements AfterContentInit, ControlValueAcces
 
         let column: PickerColumn = {
           name: key,
+          selectedIndex: 0,
           options: values.map(val => {
             return {
               value: val,

src/components/picker/picker-component.ts

@@ -512,7 +512,7 @@ export class PickerCmp {
       if (!isPresent(column.options)) {
         column.options = [];
       }
-
+      column.selectedIndex = 0;
       column.options = column.options.map(inputOpt => {
         let opt: PickerColumnOption = {
           text: '',