Sercomm Exploit module fixes

* Added targets for 8 specific targets that I've tested: Cisco WAP4410N,
Honeywell WAP-PL2 IP Camera, Netgear DG834, Netgear DG834G, Netgear
DG834PN, Netgear DGN1000, Netgear DSG835, Netgear WPNT834
* Added functionality to the CmdStagerEcho mix-in to support encoding via
octal instead of hex based on the :enc_type option. This is because many
devices would not output hex encoded values properly.
* Added options on a per-target basis for the PackFormat (endian pack()
values for communication), UploadPath (because /tmp wasn't always
writable), and PayloadEncode (previously mentioned octal encoding
option)
* Note: For some reason, some devices communicate over one endianness, but
then require a payload for the other endianess. I'm not sure what's
causing this, but if those specific combinations are not used, the
exploit fails. More research may be required for this.