Fixed account type setting; reworded IB designable message

[1ec5]

This PR fixes some regressions from #1553, as well as some bugs that’ve been lingering for longer:

• We need to look in the host app’s Info.plist, not MapboxGL.framework’s.
• Currently, if you set MGLMapboxMetricsEnabledSettingShownInApp = YES in Info.plist, you still get the assertion failure in -[MGLMapboxEvents init] because the access token is read in first, causing the shared MGLMapboxEvents to be created. This change rearranges the order that the settings are read in, since one is dependent on the other.
• Interface Builder was still showing an “Access Token” inspectable, which would’ve led to an assertion failure if set.
• The IB designable message is only relevant to developers displaying Mapbox-hosted maps, so the message should reflect that scope.
• The IB designable message can’t detect whether the access token is set in Info.plist, and it can’t detect whether a Settings bundle has been added. So I nixed the “A-OK” Mapbox blue designable screen – we just show steps to get started no matter what and point to the “First steps with Mapbox GL for iOS” guide.

Fixes #1613.

[friedbunny]

Currently, if you set MGLMapboxMetricsEnabledSettingShownInApp = YES in Info.plist, you still get the assertion failure in -[MGLMapboxEvents init] because the access token is read in first, causing the shared MGLMapboxEvents to be created. This change rearranges the order that the settings are read in, since one is dependent on the other.

Mmm, am looking at this now because it was crashing the tests. Have a couple questions:

1. Why use [MGLAccountManager sharedManager].mapboxMetricsEnabledSettingShownInApp but then self.accessToken in +[MGLAccountManager load]?
2. Why start [MGLMapboxEvents sharedManager] in +[MGLAccountManager setAccessToken:] and not at the end of +[MGLAccountManager load]?

[friedbunny]

MapViewTests pass with these changes (after applying 0c78314), thanks to the reordering of the first [MGLMapboxEvents sharedManager] call.

[1ec5]

Why use [MGLAccountManager sharedManager].mapboxMetricsEnabledSettingShownInApp but then self.accessToken in +[MGLAccountManager load]?

#1553 made +[MGLAccountManager setMapboxMetricsEnabledSettingShownInApp:] unavailable as a precursor to removing it entirely. (Although I see it’s still implemented.) As far as I can tell, there’s no way to make a method un-unavailable privately without subclassing. If you can think of a way to override the unavailable() attribute, I’m all ears!

Why start [MGLMapboxEvents sharedManager] in +[MGLAccountManager setAccessToken:] and not at the end of +[MGLAccountManager load]?

Nothing that MGLMapboxEvents does makes sense without an access token. The events API (the server API, that is) requires an access token. Moreover, Mapbox Metrics shouldn’t be active if the app is using a non-Mapbox-hosted style and tile server.

[1ec5]

Here’s what the designable looks like now in various form factors:

As you can see, I also added some additional constraints so that the designable looks more presentable when it’s too small to show everything.