Fix upload of existing files
We have updaed the way to store files in the cdn. Now, we add in the rcc filenames the date of the last git update.
However, we have noticed everytime we generate the rcc files, the md5 changes, even if the content is the same as the previous rcc (same date).
We should download the existing Contents from the cdn first, then for each file, only generate the rcc if the date has changed (optimisation, we can still generate all) and only send the updated rcc files. Also the Contents file must be merged with the existing one to keep the already uploaded rcc.