* Rename JS concepts
1. Assignment declaration -- an assignment that is treated like a
declaration. Previously called [JS] special (assignment|declaration),
among other things.
2. Expando -- a value that can be used as a target in assignment
declarations. Currently, a class, function or empty object literal.
Functions are allowed in Typescript, too. Previously called a JS
container, JS initializer or expando object.
3. JavaScript -> Javascript. This is annoying to type, and looks like
'Java Script' in a camelCase world.
Everything is a pure rename as far as I know. The only test change is
the API baselines, which reflect the rename from SymbolFlags.JSContainer
to SymbolFlags.Assignment.
* Remove TODO
* Rename Javascript->JS
Note that this introduces a variable name collision in a couple of
places, which I resolved like this:
```ts
const isInJavascript = isInJSFile(node);
```
* Use more nodelike paths for import types when possible
* move functionality from services into compiler, fix with propert file/directory conflict handling
* mark suspect cast
* Enable '--strictNullChecks'
* Fix API baselines
* Make sys.getEnvironmentVariable non-nullable
* make properties optional instead of using `| undefined` in thier type
* reportDiagnostics should be required
* Declare firstAccessor as non-nullable
* Make `some` a type guard
* Fix `getEnvironmentVariable` definition in tests
* Pretend transformFlags are always defined
* Fix one more use of sys.getEnvironmentVariable
* `requiredResponse` accepts undefined, remove assertions
* Mark optional properties as optional instead of using `| undefined`
* Mark optional properties as optional instead of using ` | undefined`
* Remove unnecessary null assertions
* Put the bang on the declaration instead of every use
* Make `createMapFromTemplate` require a parameter
* Mark `EmitResult.emittedFiles` and `EmitResult.sourceMaps` as optional
* Plumb through undefined in emitLsit and EmitExpressionList
* `ElementAccessExpression.argumentExpression` can not be `undefined`
* Add overloads for `writeTokenText`
* Make `shouldWriteSeparatingLineTerminator` argument non-nullable
* Make `synthesizedNodeStartsOnNewLine` argument required
* `PropertyAssignment.initializer` cannot be undefined
* Use one `!` at declaration site instead of on every use site
* Capture host in a constant and avoid null assertions
* Remove few more unused assertions
* Update baselines
* Use parameter defaults
* Update baselines
* Fix lint
* Make Symbol#valueDeclaration and Symbol#declarations non-optional to reduce assertions
* Make Node#symbol and Type#symbol non-optional to reduce assertions
* Make `flags` non-nullable to reduce assertions
* Convert some asserts to type guards
* Make `isNonLocalAlias` a type guard
* Add overload for `getSymbolOfNode` for `Declaration`
* Some more `getSymbolOfNode` changes
* Push undefined suppression into `typeToTypeNodeHelper`
* `NodeBuilderContext.tracker` is never `undefined`
* use `Debug.assertDefined`
* Remove unnecessary tag
* Mark `LiteralType.freshType` and `LiteralTupe.regularType` as required
* Clean up code for nonrelative path completions
* Remove unnecessary test and simplify based on that
* More code review
* Call getCompletionEntriesFromTypings unconditionally
* Apply 'no-unnecessary-initializer' lint rule
Forbids `let`/`const` statements to be initialized to `undefined`, since that's the initial value by default anyway.
The auto-fixer also happened to remove two unnecessary `as number` casts in `src/harness/parallel/worker.ts`.
For historical data: to run with `--fix`, I modified the line in `Jakefile.js` that declared the `cmd` for running TSLint.
* Moved worker.ts type assertions to parameters
