Version 2.7.0 - minor API changes !

• API change
  • client_opt: expiry and hearbeat_interval are float (Alexander Usyskin)
    wsmc_set_sub_expiry() and wsmc_set_heartbeat_interval() change their
    first parameter from int to float
  • bump so version of libwsman_client from 4 to 5
  • new functions for C++ bindings: OpenWsmanClient::GetWithFlags()
    and OpenWsmanClient::PutWithFlags to add a 'flags' parameter
    (Alexander Usyskin)
  • add FLAG_SUPRESS_100_CONTINUE to options, fixes #131 to workaround
    a curl problem. Reportedly curl 7.69.0 fixes this also in curl.
    (Alexander Usyskin)
  • fixed several compiler warnings (Alexander Usyskin)
  • fixed spelling errors (Tomas Winkler)