[SDL 0216] Widget support

[theresalech]

Proposal: Widget support

This proposal is about widget support for SDL applications on modern infotainment systems and large displays. At the same time the proposed feature should prepare SDL for multi-window and multi-display support.

Review: smartdevicelink/sdl_evolution#664

Steering Committee Decision:

The Steering Committee voted to accept this proposal with the agreed upon revisions, described in this comment and included in PR #729.

The proposal .md file was updated to reflect these revisions on 5/20/19.

[theresalech]

Proposal markdown file has been updated per the revisions included in accepted Evolution Proposal SDL 0216 Revisions - Widget Support. The revisions include changing SystemCapabilityType element name DISPLAY to DISPLAYS and specifying that proxy releases of this feature should include manager updates (to be entered as a separate proposal).
Please reference issue and markdown file for revision details.