Added digitizer_channel.delay, rf_source markers for Keysight, Tektronix

CHANGELOG.md

pulse_lib/base_pulse.py

pulse_lib/configuration/physical_channels.py

pulse_lib/examples/configuration/medium.py

pulse_lib/examples/configuration/medium_iq.py

pulse_lib/keysight/M3202A_uploader.py

pulse_lib/keysight/qs_sequence.py

pulse_lib/keysight/qs_uploader.py

pulse_lib/qblox/pulsar_sequencers.py

pulse_lib/qblox/pulsar_uploader.py

pulse_lib/tektronix/tektronix5014_uploader.py