Added most of the PID symbols

icons/pid_symbols/light/arrow.svg

icons/pid_symbols/light/burst_disk.svg

icons/pid_symbols/light/check_valve.svg

icons/pid_symbols/light/empty.svg

icons/pid_symbols/light/flexible_connection.svg

icons/pid_symbols/light/manual_valve.svg

icons/pid_symbols/light/motor_valve.svg

icons/pid_symbols/light/pressure_gauge.svg

icons/pid_symbols/light/pressure_regulator.svg

icons/pid_symbols/light/pressure_transducer.svg

icons/pid_symbols/light/quick_connector.svg

icons/pid_symbols/light/relief_valve.svg

icons/pid_symbols/light/three_way_valve.svg

icons/pid_symbols/light/vessel.svg

src/ui/panes/pid_drawing_tool/symbols.rs