Major patch for upload_folder, download_folder, upload and download

Major rework for methods and error patching:

• Binary download problem solved (now content bytes download correctly)
• Download counter and progress bar implemented (independent bar for single files and total folder content)
• Binary files now upload with extension
• convert() method reworked
• Not converted files now upload with extension
• find_duplicate() method reworked. Now it will correctly find a duplicate file even when it is binary and have an extension
• get_update() method deprecated in favour of new find_duplicate() method
• 'update' boolean option in upload() and create_subfolder() finally reworked for efficiency purpose and to work with the new methods