Convert Section Plugin to Use Sandy

Summary:
Convert section plugin to Sandy API.

TODO
- Fix layout issues
  - scrollbar occurs in small component (bottom layout)
  - scrollbar in wrong place (top layout)
  - text shrunk in bottom part of tree component
- (?) move away from d3
- better typing for payload
- move components to functional one
- unit test

Reviewed By: mweststrate

Differential Revision: D22385993

fbshipit-source-id: 862d4b775caf2d9a7bcb37446299251965a5d6db

.flowconfig

@@ -16,7 +16,7 @@
 <PROJECT_ROOT>/desktop/babel-transformer/.*
 <PROJECT_ROOT>/desktop/plugins/fb/relaydevtools/relay-devtools/DevtoolsUI.js$
 <PROJECT_ROOT>/website/.*
-<PROJECT_ROOT>/desktop/plugins/sections/d3/d3.js$
+<PROJECT_ROOT>/desktop/plugins/sections/src/d3/d3.js$
 <PROJECT_ROOT>/react-native/ReactNativeFlipperExample/.*
 
 [libs]