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.
Clean CmdStagerEcho
Make slice_up_payload easier
Update module description
Add Manual targets to sercomm_exec
Delete Netgear N150 target, ist's a Netgear DGN1000 model
Merge pull request #4 from jvazquez-r7/review_2874

Clean CmdStagerEcho and Add module targets
Delete debug comments
Land #2874, @mandreko's sercomm exploit fixes