Upgrades our build scripts to target ES2017 since they are run on modern versions of node
This allows us to remove shims for es6 features such as `Object.assign`, and also remove a few extra typings packages
Tree Shaking:
- do not proceed with tree shaking when there are compilation errors
- load .d.ts files in the language service
- adopt TS 3.1.1 in symbol resolution
- use the real tsconfig.json / with "node" resolution
Bundling:
- fix issue where files were being looked for in out-build instead of out-editor-build