[FEATURE] ClamAV/VirusTotal waiting page

[fl0ppy-d1sk]

Plugin(s)
ClamAV and VirusTotal

What's needed and why ?
With a high number and/or big uploaded files, the ClamAV/VirusTotal scan can take some time. When that's the case, we need a way to do it async and display a "waiting page" to the user until scan is finished.

We can use the ASYNC_SCAN setting with a yes or no value.