* Add workspace.fontAliasing configuration option

Add simple boolean configuration option that controls how fonts are being rendered in workbench.

Enabling this option in configuration results with more native feel on macOS.

* Add different modes for workbench.fontAliasing

Support both additional "antialiased" and "none" methods on font antialiasing. Leaving subpixel-antialiased as default

See #2577

* Apply workbench.fontAliasing on document.body

Instead of using only workbench element, apply font aliasing setting globally on entire window.

See #2577

- Workspace context service
- Workspace configuration service
- Configuration editing service
- Workspace editing service

This reverts commit df660488.

TS 2.3.1 introduced a breaking change by [switching to covariant types for callbacks](https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#covariance-in-callback-parameters). This change tries to fix these compiler errors in the workbench codebase