paper-time-picker-edit-dialog should use same input as output format

[ronnyroeller]

The element paper-time-picker-edit-dialog expects as input a property time of type String. As output it generates an event with a parameter time of type Object.

For an editor, the Input and output format should be the same to simplify the life of the consumer. This leads to these options:

1. Both Date (which would be my preferred option in the given context as this moves the whole complexity to the edit-dialog instead of the consumer of the dialog)
2. Both Object
3. Both String

[cminardi]

Both date picker and datetime picker now work with Date object.

Fixed in: 9686b2e