[FEATURE]: new palette format! (Merge of palette-branch)

This commit merges the changes we did to the palette resource object in the improved palette format branch. It includes...
- A new zip-based file format.
 - This file format can hold high-bit depth colors, and supports all the colors that Krita can process.
 - It also has support for palette groups, though the groups can not be edited inside Krita yet.
 - Support for metadata like ID, name, and whether it is a spotcolor.
- Support for loading sbz, the swatchbooker format(courtesy of L. E. Segovia/Amyspark)

With this, we can start on a nice docker for palette mangling with all sorts of new goodies :)

CCMAIL:kimageshop@kde.org
Fixes T4121
Differential Revision: https://phabricator.kde.org/D4719
Differential Revision: https://phabricator.kde.org/D3254