Expose emulator api

[Fatme]

Related to this PR: telerik/mobile-cli-lib#1101

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This PR deletes all legacy, unneeded and duplicated code that is used for working with iOS and Android emulators.

This PR adds the functionalities below:

• tns devices android --available-devices - shows all available Android genymotion and Android avd emulators (previously only avd emulators were shown)
• tns devices --available-devices - works correctly and shows all available iOS simulators, Android genymotion and Android avd emulators. (previously does not work)
• tns run android --device <imageIdentifier> - it is already possible to run on device with specified imageIdentifier (previously it can run only on emulators specified by identifier or name)

This PR exposes emulator api from devicesService. The api consists from the following two methods:

1. getAvailableEmulators(opts?: {platform?: string}) -> Returns all available and running iOS and Android emulators. The method accepts platform parameter, so the emulators can be filtered by platform. The output from the method is in the following format:

{
    ios: {
        devices: Mobile.IDeviceInfo[],
        errors: string[]
    },
    android: {
        devices: Mobile.IDeviceInfo[],
        errors: string[]
   }
}

Each available android emulator (NOTE: not running emulator) has the properties below:

{
   identifier: null,
   displayName: the name of the emulator,
   model: the same as the displayName,
   version: The android version of emulator,
   vendor: can be Avd or Genymotion,
   status: not running,
   errorHelp: additional information for errors that prevents working with this device,
   isTablet: false,
   type: Emulator,
   imageIdentifier: for genymotion emulators is the id of virtual machine and for avd is the name of .ini file
}

Each running android emulator has the properties below:

{
   identifier: the emulator identifier,
   displayName: the name of the emulator,
   model: the value of 'ro.product.model' property,
   vendor: the value of 'ro.product.brand' property,
   status: running,
   errorHelp: additional information for errors that prevents working with this device,
   isTablet: when device's 'ro.build.characteristics' property contains "tablet" word or when the 'ro.build.version.release' is 3.x,
   type: Device
   imageIdentifier: for genymotion emulators is the id of virtual machine and for avd is the name of .ini file
}

2. startEmulator(options) - Starts the specified emulator. The emulator can be specified by imageIdentifier, by name or by emulator object. For android it is possible to pass --timeout option. This option describes the timeout in miliseconds that {N} CLI will wait emulator boot to complete. It might take too long time on some machines to start native android emulator, so this option is useful in such cases.

[DimitarTachev]

missing XML comments

[DimitarTachev]

why do we register Android specific services in iOS project service?

[Fatme]

Because this tests relies on real DevicesService -

nativescript-cli/test/ios-project-service.ts

Line 82 in b1c79a4

testInjector.register("devicesService", DevicesService);

On the other hand devicesService injects androidEmulatorServices so we need it here.

[dtopuzov]

run ci

[dtopuzov]

run ci

[rosen-vladimirov]

The new API does not have documentation. Please follow the guidelines described here

[Natalia-Hristova]

run ci

[Natalia-Hristova]

run ci

[Natalia-Hristova]

run ci

[dtopuzov]

run ci

[rosen-vladimirov]

emualtors -> emulators