Create a centring plan

[DominicOram]

To centre the sample we need to do a step scan using the hexapod z. The scan should start in air and then move the sample into the beam taking a single data point at a set of steps. We should be able to configure:

• The number of steps
• The size of each step
• The exposure at each step

At each step we should put in the nexus file:

• The eiger image
• The i0 data
• The z location

We should be able to do this using https://nsls-ii.github.io/bluesky/generated/bluesky.plans.scan.html

Acceptance Criteria

• We produce a nexus file with the expected data at each step