fix: make @schematics/angular a devDependency and update to Angular 8.2

[sis0k0]

The @nativescript/schematics package uses TypeScript utility functions from @schematics/angular. The utility functions return ASTs generated from the source code. After that these ASTs are used by other functions in @nativescript/schematics.
@nativescript/schematics depends on the version of TypeScript used in the project, whereas @schematics/angular has its own dependency on TypeScript. If the versions of the two TypeScript packages don't match, we end up comparing ASTs generated from different TS versions which usually results in an error.
This PR removes the dependency of @schematics/angular from the @nativescript/schematics. That way, the version in the user's project will be used instead. We rely on the assumption that the project will have matching versions of @schematics/angular and TypeScript.

[vakrilov]

We rely on the assumption that the project will have matching versions of @schematics/angular and TypeScript.

AFAIK the @schematics/angular will does not depend on specific typescript to be used in the project. Actually, the @schematics/angular bring its [own version of typescript`](https://github.com/angular/angular-cli/blob/master/packages/schematics/angular/utility/ast-utils.ts#L8) embedded in the package. Currently we rely on the above assumption, but it is not something that angular CLI looks after.

SUGGESTION: Let's get rid of the typescript dependency too and start using the typescript embedded in @schematics/angular:

import * as ts from '@schematics/angular/third_party/github.com/Microsoft/TypeScript/lib/typescript'; 

This we will be sure that the typescript SourceFiles use the same version of TypeScript as @schematics/angular/utility/ast-utils