Mark -initWithPath: as a designated initializer

Mutes Xcode 7 warning. Marking -initWithPath: as a designated initializer is not allowed in the protocol, so we must redeclare it in the class extension.

Classes/GlobalStateExplorers/FLEXFileBrowserFileOperationController.m

@@ -13,6 +13,8 @@
 
 @property (nonatomic, copy, readonly) NSString *path;
 
+- (instancetype)initWithPath:(NSString *)path NS_DESIGNATED_INITIALIZER;
+
 @end
 
 @implementation FLEXFileBrowserFileDeleteOperationController
@@ -74,6 +76,8 @@
 
 @property (nonatomic, copy, readonly) NSString *path;
 
+- (instancetype)initWithPath:(NSString *)path NS_DESIGNATED_INITIALIZER;
+
 @end
 
 @implementation FLEXFileBrowserFileRenameOperationController