Currently, when a view is rendered and a date or datetime field is not
defined (e.g. when designing reports), it causes a JS error.
This patch fixes the above error.
This applies some changes to the module after migration, to conform new
guidelines and conventions for version 11.0.
In addition, this applies the following fixes:
- The widged didn't work when the field was a `datetime` due to a typo
in a JS conditional
- Replaced `Object.assign()` -> `_.assign()` to improve
browser-compatibility
* use include instead of extend
* add README.rst
* update api doc link in readme.rst
* remove description from __oe__ since it is in README.rst
* add OCA icon and AGPL badges
* add datepicker.js through assets_backend
Luis González
Yanina Aular
Pedro M. Baeza
Stéphane Bidoul
Markus Schneider
Vincent Vinet
Artem Kostyuk
Holger Brunn