Make "app" point configurable in component generation

[dhcdata]

angular-cli.json allows flexibility for how project structure is defined. This PR allows for the "app" to be configurable. Consider the following tree structure:

├── .
├── angular-cli.json
├── src/ (default but configurable with "root" value)
│   ├── app/ (default)
│   ├── assets
│   ├── environments
│   ├── myCustomApp/ (configurable by added "app" value)
│   ├── index.html
│   ├── [...]
├── [...]

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[baruchvlz]

You're trying to make src/app be src/{ngConfig.app[0].app} ?

[dhcdata]

Correct. This would make the "app" point configurable. When attempting to build a generic module in parallel with an specific application, this type of structure makes it easier to keep them separate.

[filipesilva]

Superseded by #4610 I think.

[dopry]

@filipesilva I do not think it is infact superceded by #4610, I think they're the similar and parts of a whole.

[dhcdata]

ng new command creates the project with src/app. Once that's done and #4610 is merged, identifying the "mount-ish" point is irrelevant.

Adding a flag for ng new might be beneficial but is outside the scope of where this PR went.

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