add header docs for new MGLAccountManager; reorg

include/mbgl/ios/MGLAccountManager.h

@@ -1,10 +1,29 @@
 #import <Foundation/Foundation.h>
 
+/** The MGLAccountManager object provides a global way to set a Mapbox API access token, as well as other settings used framework-wide. */
 @interface MGLAccountManager : NSObject
 
-+ (void) setMapboxMetricsEnabledSettingShownInApp:(BOOL)showsOptOut;
-+ (BOOL) mapboxMetricsEnabledSettingShownInApp;
-+ (void) setAccessToken:(NSString *) accessToken;
-+ (NSString *) accessToken;
+/** @name Authorizing Access */
+
+/** Set the Mapbox API access token for the framework.
+*
+*   You can set an access token on MGLAccountManager or on an individual map view. The same token is used throughout the framework.
+*   @param accessToken The Mapbox API access token. */
++ (void)setAccessToken:(NSString *)accessToken;
+
+/** Retreive the Mapbox API access token for the framework.
+*
+*   You can set an access token on MGLAccountManager or on an individual map view. The same token is used throughout the framework.
+*   @return accessToken The Mapbox API access token. */
++ (NSString *)accessToken;
+
+/** @name Providing User Metrics Opt-Out */
+
+/** Certain Mapbox plans require the collection of user metrics. If you aren't using a preference switch in an existing or new `Settings.bundle` in your application, set this value to `YES` to indicate that you are providing a metrics opt-out for users within your app's interface directly.
+*   @param showsOptOut Whether your application's interface provides a user opt-out preference. The default value is `NO`, meaning a `Settings.bundle` is expected for providing a user opt-out preference. */
++ (void)setMapboxMetricsEnabledSettingShownInApp:(BOOL)showsOptOut;
+
+/** Whether in-app user metrics opt-out is configured. If set to the default value of `NO`, a user opt-out preference is expected in a `Settings.bundle` that shows in the application's section within the system Settings app. */
++ (BOOL)mapboxMetricsEnabledSettingShownInApp;
 
 @end