Investigate using Externally Interrupted Exposure Series

In the future having to re-arm the Eiger between XRC and rotation data will likely become a bottleneck. It may be possible to avoid this bottleneck by using the Externally Interrupted Exposure Series mode of the Eiger. To investigate this we will need to:
* Ensure the only difference in Eiger settings between XRC and rotation is the exposure time
* Ensure we can set the Eiger into this mode
* Test taking one collection that contains data at different exposures

Note: We will have to think about the bit depth of the data. XRC uses 16 bit as we're doing small exposures, rotations sometimes use 32. The manual implies the data will come out with a bit depth based on what exposure time we estimate prior to arm so we will need to set it to something that covers both XRC and rotation. Therefore this may only work on rotation collections with small exposures - needs further discussion.