Improve cryptext integration

Currently, our cryptext integration is really minimal:
The only thing that is supported is doubleclicking on a '.cer' file.

• Add support for other extensions (.crt, .pem, ...)
• Add an icon (use an icon from cryptui.dll)
• Add a 'friendly name' (should be a resource string inside cryptext)

Here is the .cer registered:
https://git.reactos.org/?p=reactos.git;a=blob;f=boot/bootdata/hivecls.inf;hb=5bfe6a5376cf3145ece2ce9d7f790b31ec23684e#l80