Add Dropper category and add CurlNexec into it

[ariary]

What is dropper tools category?

A dropper is a kind of Trojan that has been designed to "install" some sort of malware (virus, backdoor, etc.) to a target system.

I think this kind of tools could not be placed into other category and are part of the arsenal of a pentester

What is curlNexec?
curlNexec could be used as a stealth dropper (for Unix). It enable us to retrieve a remote binary file and execute it in one step.

• The binary file is not mapped into the host file system
• The execution program name could be customizable
• Bypass 3rd generation firewall could be done with http3 support

[ariary]

see #426