fix(install): ng install should work with local npm package archives

[jeffbcross]

In order to test packages locally, it'd be nice to run: ng install some-local-package.tar.gz. Though npm install succeeds with this method, the install process is treating "some-local-package.tar.gz" as the package name, which causes later steps of ng install to fail. Instead, ng install should parse the name from package.json after the package is installed.

[hansl]

We're going to use npm directly in ng install. Closing this as this will be addressed. Once ng install is done we can revisit this.

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