Made lat/lon/zoom inspectable

Declared these IB-specific inspectables in a separate category that developers are not expected to import. Currently these inspectables are order-dependent due to #1181.

Ref #929

include/mbgl/ios/MGLMapView+IBAdditions.h

@@ -0,0 +1,29 @@
+#import "MGLMapView.h"
+
+@interface MGLMapView (IBAdditions)
+
+// Core properties that can be manipulated in the Attributes inspector in
+// Interface Builder. These redeclarations merely add the IBInspectable keyword.
+// They appear here to ensure that they appear above the convenience properties;
+// inspectables declared in MGLMapView.h are always sorted before those in
+// MGLMapView+IBAdditions.h, due to ASCII sort order.
+
+@property (nonatomic) IBInspectable NSString *accessToken;
+@property (nonatomic) IBInspectable NSString *mapID;
+
+// Some convenience properties related to the initial viewport. These properties
+// are not meant to be used outside of Interface Builder. latitude and longitude
+// are backed by properties of type CLLocationDegrees, but these declarations
+// must use the type double because Interface Builder is unaware that
+// CLLocationDegrees is a typedef for double.
+
+/// Initial latitude at which the receiver is centered.
+@property (nonatomic) IBInspectable double latitude;
+
+/// Initial longitude at which the receiver is centered.
+@property (nonatomic) IBInspectable double longitude;
+
+/// Initial zoom level of the receiver.
+@property (nonatomic) IBInspectable double zoomLevel;
+
+@end

include/mbgl/ios/MGLMapView.h

@@ -39,9 +39,8 @@ IB_DESIGNABLE
 
 /** @name Authorizing Access */
 
-/** Sets a Mapbox API access token for the map view. 
-*   @param accessToken A Mapbox API token. */
-@property (nonatomic) IBInspectable NSString *accessToken;
+/** Mapbox API access token for the map view. */
+@property (nonatomic) NSString *accessToken;
 
 #pragma mark - Managing Constraints
 
@@ -166,10 +165,11 @@ IB_DESIGNABLE
 /** @name Styling the Map */
 
 /** Mapbox map ID of the style currently displayed in the receiver, or `nil` if the style does not have a map ID.
- 
-    The style may lack a map ID if it is located at an HTTP, HTTPS, or asset: URL. Use -styleURL to get the URL in these cases.
- */
-@property (nonatomic) IBInspectable NSString *mapID;
+*
+*   The style may lack a map ID if it is located at an HTTP, HTTPS, or local file URL. Use `styleURL` to get the URL in these cases. 
+*
+*   To display the default style, set this property to `nil`. */
+@property (nonatomic) NSString *mapID;
 
 /** Returns the URLs to the styles bundled with the library. */
 - (NSArray *)bundledStyleURLs;