Fixed backup import / export

*** NOTICE FOR ANDROID USERS WITH VERSION 10 AND ABOVE ***

Due to limited management of file system access, the user is asked where to save the backup and where to retrieve it

The import and export functions are present in the 'Calendar' section

>>> When you choose to create a backup you are asked where to save the file in the internal memory

>>> When you want to import, you are asked to choose a file from the internal memory