Better files filtering in Dokeos 1.8.5

It's already in the code for Dokeos 1.8.5 since 2 weeks ago: files extensions filtering. It was possible, in 1.8.4, to filter files extensions coming from ZIP files, but I didn't have time back then to include a widespread file filtering. It is included now. There is still a problem whereby Windows interprets files looking inside them, so it does not need the extension to be wrong in order to execute the file as is needed for a virus to spread. This is not yet filtered in Dokeos, so we are looking into integrating an (old) extension called "virusscanner" on our extensions page so that we cover that point as well. That extension connects to the ClamAV database to check the uploaded file for any trace of virus. The problem with all that is still that some human minds prefer self interest to common interest, and take time to spread their viruses all around so we have to spend time fighting them. Humans vs humans is a tougher battle than machine vs machine.