`org-store-link-props` is is obsolete since Org-mode 9.3.

This commit use `org-link-store-props` when available, else it use the
old `org-store-link-props`.

This commit also call the `org-link-store-props` function with the
`funcall` function instead of `apply` and remove the cl-loop on extra
properties.

`elfeed-link-store-link` store some more properties when the buffer is
on mode `elfeed-link-store-link`.

These properties are pre-processed, as required by
`org-link-store-props`.

The new properties are:
- `title`              : Feed entry title
- `external-link`      : Feed entry external link
- `date`               : Date time of the feed entry publication, in
                         full ISO 8601 format
- `authors`            : List of feed entry authors names, joint by a
                         comma
- `tags`               : List of feed entry tags, in Org-mode tags
                         format
- `content`            : Content of the feed entry
- `feed-title`         : Title of the feed
- `feed-external-link` : Feed external link
- `feed-authors`       : List of feed authors names, joint by a comma

If `content` type is HTML, it is automatically embedded into an
Org-mode HTML quote.

Document the compatibility of Elfeed and `org-store-link` and
`org-capture`.

List properties accessible from Org-capture template.

`org-link-store-props`, when we store a date property, automatically
generate a 2 new properties:
- `date-timestamp`          : The date and time in Org-mode active timestamp
                              format
- `date-inactive-timestamp` : The date and time in Org-mode inactive
                              timestamp format