Write tests for nativescript-cli/issues/1548 #116

Write tests for NativeScript/nativescript-cli#1548

What to check:

• If no simulators are running we start the correct one when we pass sdk and device options.
• If simulator is running and we specify another one we should start it (and keep the previous open).

We should be careful for this when writing tests:

• For some tests we need specific simulator because we compare images (livesync tests).
• If we start another one we should ensure default we need is started before other tests.
• If should stop simulator we start at some point (we need to get as less resources on the machine as we can and for sure we should kill all the simulators when all tests are complete).