initial artboards for icons in design.ai

MDPI (160DPI), HDPI (240DPI), XHDPI (480DPI), XXHDPI (480DPI), XXXHDPI
(640DPI)
Revert "initial artboards for icons in design.ai"

This reverts commit 9a6c612ff91b8f5fb78640b09f17c86a2e33128a.