Initial commit of spread-sheet-widget
Initial commit of GNU Spread Sheet Widget.
I know that typically Solus doesn't allow pre-release software to be included, but SSW is required for GUI support in PSPP 1.2.0.
Test Plan: Built PSPP 1.2.0 against it and tested the GUI.
Reviewers: Triage Team, JoshStrobl
Reviewed By: Triage Team, JoshStrobl
Differential Revision: https://dev.getsol.us/D7227