install NgRx dependencies if using --init

[jessesanders]

Describe the bug
When using the init flag, the schematic should check for NgRx libraries in the package.json, add missing libraries, and run npm install.

To Reproduce
Steps to reproduce the behavior:

1. ng new my-project
2. ng add @briebug/ngrx-entity-schematic customer --path=src/app/state --init
3. ng build

Expected behavior
schematic should check for NgRx libraries in the package.json, add missing libraries, and run npm install so that no additional steps are needed.

Desktop (please complete the following information):

• OS: Mac OS
• Angular CLI Version 7.2.4