#60565

In these cases, the programmer has explicitly indicated that the type should be nullable

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

#50556

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

* Pick up TS 2.7

* Fix formatter in build script

* Fix build error for ts 2.7

* Pick up new ts format and tslint versions

* Update lock

* use 2.7.2 for build

* Formatting

* Pick up TS 2.7

* Fix formatter in build script

* Fix build error for ts 2.7

* Pick up new ts format and tslint versions

* Update lock

* use 2.7.2 for build

* Formatting