An error description now returns as a base64-encoded string
Added an extended code status to the error response ( function SendError() ).
It returns:
    - an exit code of an external program in case of functions linux-ipaddr-*
    - an unsigned number (errno) describing an error condition
    - and "-1" in case if an extended code is not defined
Added the function GetDefaultGateways(). It returns list of default gateways for IPv4/IPv6 families
Updated the commands documentation
Updated README.md
v0.2