ENH: pick apart 'standard' scans
ENH: pick apart 'standard' scans

Add pre/post scan hooks and the ability to add to the call signature.

This is to allow DScans to output to OLog the initial position.

Closes #130

ericdill/bluesky,sameera2004/bluesky,dchabot/bluesky,ericdill/bluesky,sameera2004/bluesky,klauer/bluesky,dchabot/bluesky,klauer/bluesky