Migrate to @react-native-community/react-native-datetimepicker

[mmazzarolo]

This PR was previously available at #262

This PR captures the work needed to migrate to the new @react-native-community/react-native-datetimepicker.

Setup:

• Added @react-native-community/react-native-datetimepicker
• Updated the dependencies
• Updated the example

IOS:

• Implemented @react-native-community/react-native-datetimepicker
• Simplified the API, removed a few style props (users can still supply their own version of the header/buttons)
• Find a workaround to this RN issue, easily reproducible by touching the picker without changing the selected value
• Moved out of react-native-modal

Android:

• Implemented @react-native-community/react-native-datetimepicker
• Simplified the API

Docs:

• Update README.md

Deprecated props:
A few prop names are going to be changed (the old name will still work though).
- titleIOS → headerTextIOS
- customTitleContainerIOS → customHeaderIOS
- onHideAfterConfirm → onHide
- customDatePickerIOS → customPickerIOS

Breaking changes:
The following props are not supported anymore:

• cancelTextStyle → Please use customCancelButtonIOS to override the component instead
• confirmTextStyle → Please use customConfirmButtonIOS to override the component instead
• datePickerModeAndroid → Please use the display prop of @react-native-community/react-native-datetimepicker instead
• dismissOnBackdropPressIOS → This is now the default behaviour on iOS
• hideTitleContainerIOS → Please set customHeaderIOS to null instead
• neverDisableConfirmIOS→ This behaviour was causing a few issues with the new picker
• pickerRefCb→ Not supported by the new picker
• reactNativeModalPropsIOS → react-native-modal is not being used anymore