Support reading `java.util.Calendar` / `java.util.Date` from textual serialization

Hi,

I'm writing a list of instances of my class that has a calendar field.

```
File file = new File(context.getFilesDir(), fileName);
try {
JSON.std.write(listOfObjects, file);
```

Writing works just fine, but when reading the created json, I receive the following exception:

`com.fasterxml.jackson.jr.ob.JSONObjectException: Can not get long numeric value from JSON (to construct java.util.Calendar) from JSON String
`

I can fix this easily by adding the `JSON.Feature.WRITE_DATES_AS_TIMESTAMP`to the writer, but I find it rather odd that jackson-jr is not able to read what it has written with complete default configuration.

I'm using `'com.fasterxml.jackson.jr:jackson-jr-objects:2.7.4'`