Nav service route cancel

[RHenigan]

Fixes #229

This pull request [adds new content].

Summary of Changes

This PR adds a section to the Introduction for Video Streaming for Navigation apps instructing the developer to cancel their route if the navigation service becomes inactive

[NicoleYarroch]

I left a comment. I saw that the iOS code snippet is missing but I thought I would wait on creating it until my question was answered.

[RHenigan]

@joeljfischer I moved the changes back to the Video Streaming for Navigation Apps section, is there a need for an iOS code snippet?

[joeljfischer]

Suggested change

	## Canceling the Route
	## When to Cancel Your Route

[joeljfischer]

Suggested change

	Between your navigation app and the embedded navigation app, only one route should be in progress at a time. When your navigation service is no longer the active service your app will need to cancel its route.
	Between your navigation app, other navigation apps, and embedded navigation, only one route should be in progress at a time. To know when the embedded navigation or another navigation app has started a route, [create a navigation service](Other SDL Features/Creating an App Service) and when your service becomes inactive, your app should cancel any active route.

[joeljfischer]

The suggestions are messing up. Please take the raw code of this and insert it here.

@![iOS]

Objective-C

[self.sdlManager.systemCapabilityManager subscribeToCapabilityType:SDLSystemCapabilityTypeAppServices withUpdateHandler:^(SDLSystemCapability * _Nullable capability, BOOL subscribed, NSError * _Nullable error) {
    SDLAppServicesCapabilities *serviceCapabilities = capability.appServicesCapabilities;
    for (SDLAppServiceCapability *serviceCapability in serviceCapabilities.appServices) {
        if ([serviceCapability.updatedAppServiceRecord.serviceManifest.serviceName isEqualToString:<#Your service name#>]) {
            if (!serviceCapability.updatedAppServiceRecord.serviceActive) {
                // Cancel your active route
            }
        }
    }
}];

Swift

sdlManager.systemCapabilityManager.subscribe(capabilityType: .appServices) { (systemCapability, subscribed, error) in
    guard let serviceCapabilities = systemCapability?.appServicesCapabilities?.appServices else { return }
    for serviceCapability in serviceCapabilities {
        if serviceCapability.updatedAppServiceRecord.serviceManifest.serviceName == <#Your service name#> {
            if !serviceCapability.updatedAppServiceRecord.serviceActive.boolValue {
                // Cancel your active route
            }
        }
    }
}

!@