package/libelementary: move to package directory

As discussed on the list the two remaining packages in
package/efl subdirectory will be moved to package/
directory.

- Add the efl dependency to libelementary.
- Set LIBELEMENTARY_VERSION with the version number
  directly.

Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>