We compile using the alwaysStrict flag so these directives are not needed

This part removes most `use strict` directives that are right after the file header

There are many places in the code that do `import Event, { ...} from '.../event'`.

Use a configuration event that can answer if a configuration has changed or not given a resource and override identifier.
Requested configuration can be full key or section

- CLean up: Separate models and interfaces

- API to get a value given a key
- API to update value smartly
- Fine grained configuration change event
- Smart reload API
- Remove unnecessary APIs

This reverts commit 838d4a33.

- Provide folder specific keys

* Fix more Compiler Errors for TS 2.4 in the VSCode codebase

* Fix compile error for 2.3

- language
- resource

- Refactor configuration services to read settings from multiple folders
- Implement merging strategy for multi root workspace settings
- Implement a configuration model that can be reused across layers
- Implement getRoot API in workspace context service

- Use '[...identifiers]` as key