Updates needed to run on-site

• ability to set scan parameters before scans start (#71)
• acu.generate_scan accepts an az_speed and az_accel those need to be configurable (and the defaults should be 1 deg/s and 1 deg/s**2.)
• seq.scan already assumes we're at a starting point while acu.generate_scan is happy to move us to the starting point. It'd be good to be able to look at the middle of the scan for detector setup and then move to the edge, especially when the edge is close to the sun
• smurf.stream needs to accept subtype as well as tag and seq.scan needs to pass those along.

Start by reading issue #71, then inspect acu.generate_scan, seq.scan, and smurf.stream. The work is done when scan parameters and azimuth defaults are configurable, scans can be inspected before moving to the edge, and subtype is accepted and propagated alongside tag.