v4.1.12172.0-Beta2

• Transactional save operations are now supported by the Engine core. Microsoft Office, AutoCAD can now save documents, no file system monitoring or external storage is required. The sample code was simplified and refactored. The virtual Drive sample is now using a remote storage ID.
• A new dictionary-based custom properties system is provided. Now custom data of unlimited size can be associated with any file and survive transactional save operations. 
• New CustomStateHandler implemented. Windows Explorer now requests properties via web sockets when properties are requested by Windows Explorer.
• The file content was blocked for writing when IFile.WriteAsync() method is called. Now file content is not blocked for writing anymore. Microsoft Office Word file content can be synced to the remote storage on every Microsoft Word save or on unlocking event. All samples are now configured to save content to remote storage on every update.
• The FilteredDocsMonitor class is removed from the sample code. Now when the item needs to be converted back to the placeholder after MS Office/AutoCAD transactional save operation or after the removal of the attributes (typically by Notepad++), the IFolder.CreateFileAsync() method is called by the Engine.
• The IClientNotificationsWindows.UpdateAsync() call now can throw ClientLockFailedException exception if the item is being created/updated/locked/unlocked from another thread. Previously the UpdateAsync() call just logged the message. Now both IClientNotificationsWindows.CreateAsync() and IClientNotificationsWindows.UpdateAsync() methods have identical ClientLockFailedException semantics.