ranker: models addition

* Adds model for rnkSELFCITEDICT and rnkCITATIONLOG tables.

* Fixes a typo in RnkMETHOD model.

Signed-off-by: Mateusz Susik <mateuszsusik@gmail.com>
Reviewed-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
authorids: models addition

* Adds models for aidDENSEINDEX and aidINVERTEDLISTS tables.
  (addresses #1790)

* Refactors the indentations.

Signed-off-by: Mateusz Susik <mateuszsusik@gmail.com>
Reviewed-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
authorlist: initial release

* Adds new module inside `/invenio/invenio/modules` for authorlist.

* Adds SQLAlchemy models for 6 new tables. (closes #1891)

Signed-off-by: Mateusz Susik <mateuszsusik@gmail.com>
Reviewed-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>