Add TimePicker modes

Summary:
In the spirit of #10932, I added the `mode` option to the `TimePicker` Android API.
There is only one mode available for **Android < 5**, the `spinner` one.
If we are on **Android >= 5** we can choose between `spinner` or `clock`. If we specify `default` it will use the default of the current Android version.

On **Android < 5**, whatever we choose it will be this:
![screen shot 2017-02-14 at 17 05 44](https://cloud.githubusercontent.com/assets/5436545/22937805/024ec67e-f2da-11e6-8b32-a680d9bc2247.png)

On **Android >= 5**, with the `spinner` mode:
![screen shot 2017-02-14 at 16 51 17](https://cloud.githubusercontent.com/assets/5436545/22937803/024e0bbc-f2da-11e6-9f4b-26102ff2eeac.png)

And with the `clock` mode, the default:
![screen shot 2017-02-14 at 16 51 02](https://cloud.githubusercontent.com/assets/5436545/22937804/024e64e0-f2da-11e6-9911-4135049f4726.png)
Closes https://github.com/facebook/react-native/pull/12384

Differential Revision: D6006689

Pulled By: hramos

fbshipit-source-id: fcd37c867c4061b9982b1687f2c10211e54df7cf

Libraries/Components/TimePickerAndroid/TimePickerAndroid.android.js

@@ -44,6 +44,10 @@ class TimePickerAndroid {
    *   * `is24Hour` (boolean) - If `true`, the picker uses the 24-hour format. If `false`,
    *     the picker shows an AM/PM chooser. If undefined, the default for the current locale
    *     is used.
+   *   * `mode` (`enum('clock', 'spinner', 'default')`) - set the time picker mode
+   *     - 'clock': Show a time picker in clock mode.
+   *     - 'spinner': Show a time picker in spinner mode.
+   *     - 'default': Show a default time picker based on Android versions.
    *
    * Returns a Promise which will be invoked an object containing `action`, `hour` (0-23),
    * `minute` (0-59) if the user picked a time. If the user dismissed the dialog, the Promise will