Remove shared/ folder

We changed plans from moving web worker compatible code to shared/
to enforcing layers using core/, common/, ui/ and public/. This
change moves files back from the shared/ dir to clean up the
codebase.

Part of #1507

src/renderer/ColorManager.ts

@@ -3,8 +3,7 @@
  * @license MIT
  */
 
-import { IColorManager } from './Types';
-import { IColor, IColorSet } from '../shared/Types';
+import { IColorManager, IColor, IColorSet } from './Types';
 import { ITheme } from 'xterm';
 
 const DEFAULT_FOREGROUND = fromHex('#ffffff');