New features:
- ConsoleMixin: vm_screenshot, wait_for_vm_tools, get_vm_tools_status
- SerialPortMixin: setup_serial_port, get_serial_port, connect_serial_port,
clear_serial_port, remove_serial_port
Enables:
- VM console screenshots via vSphere HTTP API
- VMware Tools status monitoring and wait utilities
- Network serial ports for headless VMs and network appliances
README rewritten with comprehensive documentation of all 94 tools.
