Upload-form is currently not sanitized and is a possible security-threat

[Tobias Baldauf]

When invoking "woof -U", a simple webserver is activated that gives users an upload-form where they can easily send the host of that webserver a file.

The upload-form is not sanitized in any way, meaning that it poses a severe security.threat to the host of a "woof -U"-webserver because everything that comes through that upload-webform is directly put onto the host's machine.

We should run some tests as to the extent of that threat (code-execution via formfield, etc,) and sanitize accordingly. Incoming files should possibly also be modified (execution-bit revoked and such) so that they cannot pose a threat to the host-system without action from the receiving party.