v1.9

• spp driver: add closing timeout.
  This is an important fix. Previously device_d was stopping spp program with SIGTERM immediately after closing its output. As a result graphene program sometimes failed to exit properly, leaving broken databases. Now -close_timeout parameter for spp driver is introduced with default value 5s.
• Do not close unused devices when closing a client connection.
  The idea is to keep devices connection permanently while clients can connect and disconnect. I do not remember reason why I was closing devices here. It could be that for some bad devices/drivers keeping connection for a long time can cause problems.
  Mayby some regular and configurable cleanup procedure for device connections should be done in the future.
• Explicitely close devices when stopping device manager.
  This is a redundant measure (devices are stopped anyway), it is needed only to have consistent open-close messages in logfiles.
• Add driver serial_hm310t for Hanmatec HM310T power supply.
  This is a special driver which introduces its own scpi-like language on top of device-specific Modbus binary communication protocol. (Previously I was using separate spp programs for implementing high-level text communication)
• add missing BuildPreReq: rpm-build-tcl when building for Altlinux.
• debian/rules: strip binary files when building for Debian.
• update tests for new wget and libcurl.
• update Readme.md.