Adds VS App Center analytics + crash reporting

Currently tracks install, refresh, and update app events.

Pods/AppCenter/AppCenter-SDK-Apple/iOS/AppCenter.framework/Headers/MSLog.h

@@ -0,0 +1,73 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+#ifndef MS_LOG_H
+#define MS_LOG_H
+
+#import <Foundation/Foundation.h>
+
+@class MSDevice;
+
+@protocol MSLog <NSObject>
+
+/**
+ * Log type.
+ */
+@property(nonatomic, copy) NSString *type;
+
+/**
+ * Log timestamp.
+ */
+@property(nonatomic, strong) NSDate *timestamp;
+
+/**
+ * A session identifier is used to correlate logs together. A session is an abstract concept in the API and is not necessarily an analytics
+ * session, it can be used to only track crashes.
+ */
+@property(nonatomic, copy) NSString *sid;
+
+/**
+ * Optional distribution group ID value.
+ */
+@property(nonatomic, copy) NSString *distributionGroupId;
+
+/**
+ * Optional user identifier.
+ */
+@property(nonatomic, copy) NSString *userId;
+
+/**
+ * Device properties associated to this log.
+ */
+@property(nonatomic, strong) MSDevice *device;
+
+/**
+ * Transient object tag. For example, a log can be tagged with a transmission target. We do this currently to prevent properties being
+ * applied retroactively to previous logs by comparing their tags.
+ */
+@property(nonatomic, strong) NSObject *tag;
+
+/**
+ * Checks if the object's values are valid.
+ *
+ * @return YES, if the object is valid.
+ */
+- (BOOL)isValid;
+
+/**
+ * Adds a transmission target token that this log should be sent to.
+ *
+ * @param token The transmission target token.
+ */
+- (void)addTransmissionTargetToken:(NSString *)token;
+
+/**
+ * Gets all transmission target tokens that this log should be sent to.
+ *
+ * @returns Collection of transmission target tokens that this log should be sent to.
+ */
+- (NSSet *)transmissionTargetTokens;
+
+@end
+
+#endif