Reminder: when we next update ITK, see about disabling its readers

[mathturtle]

We just had an issue with VTK and ITK's HDF5 reader libraries conflicting due to improper mangling. VTK fixed its mangling, but when we next update ITK we should see if we can disable the readers to avoid potential issues like this (we don't use them). This may also be less an issue in future with the external pipeline. Creating this issue as a reminder.

[psavery]

@cryos I did not see this issue unfortunately at the time of my builds. This would probably need to be done before we merge #285, to avoid the HDF5 conflicts. This might also reduce the binary size.

We can update the build instructions with cmake definitions to turn off specific readers, and then re-build them all. The cmake instructions need to be updated in these places:

windows
mac
linux