PLDMTOOL : Implement a PLDM requester tool.

Implemented a way for sending PLDM requests for specific PLDM commands.
This tool will interact with MCTP daemon using UNIX domain socket, The
response got from socket will be displayed on the console in raw format.

Tested following PLDM commands:
    1) GetPLDMTypes
    2) GetPLDMVersion

Tested : Verified the RAW response data.

./pldmtool -c GetPLDMTypes
Encoded request succesfully : RC = 0
Request Message:
08 01 9b 00 04 00 00
Success in creating the socket : RC = 3
Success in connecting to socket : RC = 0
Success in sending message type as pldm to mctp : RC = 0
Write to socket successful : RC = 7
Total length:7
Loopback response message:
08 01 9b 00 04 00 00
On first recv(),response == request : RC = 0
Total length: 14
Shutdown Socket successful :  RC = 0
Socket recv() successful : RC = 0
Response Message :
08 01 00 00 04 00 01 00 00 00 00 00 00 00

./pldmtool -c GetPLDMVersion base
PLDM Type requested : base
Encoded request succesfully : RC = 0
Request Message:
08 01 9b 00 03 00 00 00 00 01 00
Success in creating the socket : RC = 3
Success in connecting to socket : RC = 0
Success in sending message type as pldm to mctp : RC = 0
Write to socket successful : RC = 11
Total length:11
Loopback response message:
08 01 9b 00 03 00 00 00 00 01 00
On first recv(),response == request : RC = 0
Total length: 15
Shutdown Socket successful :  RC = 0
Socket recv() successful : RC = 0
Response Message:
08 01 00 00 03 00 00 00 00 00 05 f1 f0 f0 00

./pldmtool -h
PLDM requester tool for OpenBMC
Usage: ./pldmtool [OPTIONS] —command... [GetPLDMTypes] [GetPLDMVersion] SUBCOMMA                                                                             ND

Positionals:
  —command TEXT ... REQUIRED
                              PLDM request command
  GetPLDMTypes TEXT           Get PLDM Type
  GetPLDMVersion TEXT         Get PLDM Version

Options:
  -h,--help                   Print this help message and exit
  -c TEXT ... REQUIRED        PLDM request command

Subcommands:
  BASE                        PLDM Command Type = BASE
  BIOS                        PLDM Command Type = BIOS
  OEM                         PLDM Command Type = OEM

Signed-off-by: Lakshminarayana R. Kammath <lkammath@in.ibm.com>
Change-Id: I758b5f5cf03ad9b91ce47144fe46cd79b41381f3