* for several options that are saved in .angular-cli.json, I've added an explanation of what setting in the json file controls that options.
* added an explanation about what --dry-run will output.
* added possible values for --style option
* added respective documentation in the command
* also added less, sass and styl(stylus) as possible style extensions
The motivation for this change is that sometimes people would want to change some of the settings set by the cli durig ng new, that they might have not known or cared about, for example, prefix.
BREAKING CHANGE: Removing the `ng init` & `ng update` commands because their current implementation causes more problems than it solves. Once RC is released, we won't need to use those to update anymore as the step will be as simple as installing the latest version of the CLI.
