• Implemented serialports command
• Allowed to put special build flags only for src files via
  srcbuild_flags environment option
• Allowed to override some of settings via system environment variables
  such as: $PIOSRCBUILD_FLAGS and $PIOENVS_DIR
• Added --upload-port option for platformio run command
• Implemented (especially for SmartAnthill)
  platformio run -t uploadlazy target (no dependencies to framework libs,
  ELF and etc.)
• Allowed to skip default packages via platformio install --skip-default-package flag
• Added tools for Raspberry Pi platform
• Added support for Microduino and Raspduino boards in atmelavr platform