This adds the initial boilerplate code that is required to introduce
the new spreadsheet editor. The editor is still hidden from the ui.
It can be made visible by undoing the change in `rna_screen.c`.
This patch does not contain any business logic for the spreadsheet editor.
Differential Revision: https://developer.blender.org/D10645
Ref T86279.
Before committing D10224, bundled preset names that are lowercase need
updating to title case for display in the UI. This changes several of
the preset file names to title case, and fixes a couple of other naming
issues in the preset names. A few strings in the code are also changed
to reflect the new filename of the Blender keymap.
