2.12.0 release notes updates

[Galen Charlton]

Catch-all bug for various changes to make to the release notes before 2.12.0 is released.

Two things so far:

[1] Add the following to the list of institutions that have sponsored development:

* Bibliomation
* British Columbia Libraries Cooperative
* C/W MARS
* Georgia PINES
* MassLNC
* Pennsylvania Integrated Library System
* Pioneer Library System

[2] s/Georga/Georgia/

[Kathy Lussier (klussier)]

I'm going to create a collab branch to track 2.12 release note changes, including those from this bug and from bug 1667283. I contacted a couple of other people and have two additions for sponsored development.

* Linn Libraries Consortium
* King County Library System

We also should add Sigio to the list since some of Dyrcona's work was done under the his Sigio hat instead of his C/W MARS hat.

[Kathy Lussier (klussier)]

I've created a collab branch at working/collab/kmlussier/2_12RC_release_note_additions that includes the above plus,

 - makes the changes discussed in bug 1667283
 - adds Jeff Davis' update to the ebook integration release note entry
 - adds contributors that were authors of patches since the beta release

I haven't done a full proofreading of the release notes yet.

[Kathy Lussier (klussier)]

Adding a note that I also need to check for translators to be added in the acknowledgements.