[TIMOB-26093] Integrate Karma unit test runner into SDK

This ticket is about integrating the [titanium-karma-runner](https://github.com/appcelerator/titanium-karma-runner) into the SDK. Ideally we should go with an approach like the following: * The above standalone Titanium Karma runner app is intended for testing libraries that are not part of any Appc project, like [titanium-vdom](https://github.com/appcelerator/titanium-vdom) for example. * For app and module projects, Introduce a new test command that will run unit tests using the Titanium Karma client. This could either be a new flag to the run command like appc run --unit or a separate command like appc test. What needs to be done: * (/) Bundle the Titanium Karma client and place it somewhere in the SDK so it can replace a project's default app.js during unit testing. (Implemented as a node module here: [titanium-karma-client](https://github.com/appcelerator/titanium-karma-client)) * Implement the appc test command. This will start a local Karma server, build the project with the altered app.js, then launches the app and passes the URL of the Karma server so tests can be executed. * (/) Create the karma-titanium-launcher which will start test run execution by passing the Karma server URL to the build testing app. (Implemented as a Karma plugin: [karma-titanium-launcher](https://github.com/appcelerator/karma-titanium-launcher)) * Nice to have: Maybe integrate with device farms?