Mac: New sites.

[MOVED]     Creation of new elements moved to shared code.
[FIXED]     When switching user, unset active key.
[FIXED]     Synchronize content calculation to avoid race issues while typing.
[ADDED]     Ability to create new sites.
[FIXED]     Unset active element when hitting backspace or escape.

MasterPassword/ObjC/MPAppDelegate_Store.h

@@ -25,6 +25,8 @@ typedef enum {
 + (BOOL)managedObjectContextPerformBlockAndWait:(void (^)(NSManagedObjectContext *))mocBlock;
 
 - (UbiquityStoreManager *)storeManager;
+
+- (void)addElementNamed:(NSString *)siteName completion:(void (^)(MPElementEntity *element))completion;
 - (MPImportResult)importSites:(NSString *)importedSitesString
             askImportPassword:(NSString *(^)(NSString *userName))importPassword
               askUserPassword:(NSString *(^)(NSString *userName, NSUInteger importCount, NSUInteger deleteCount))userPassword;