Two different processes produce .clu.1 files

[nickponvert]

There are currently two different ways for .clu.1 files to be produced, which could potentially cause confusion.

1. These files are created by klustakwik when you cluster a session
2. When we cluster multiple sessions, the resulting .clu.1 file that klustakwik makes corresponds to the entire set of spikes across all sessions. To make loading individual sessions easier, we use this multisession .clu.1 file (and the vector of which spikes came from which recording) to save individual .clu.1 files for each session.

Pros of this method: Data loading functions can just look for the .clu.1 file and load it, without having to care if the session was clustered on its own or as part of a multisession clustering run.

Cons of this method: You don't know which sessions were clustered to produce a .clu.1 file. More problematically, multiple different multisession clustering runs containing a session will overwrite the previously-existing .clu.1 file. This happens pretty frequently when you are doing some online clustering with a subset of sessions, and then doing offline clustering later with the full set of sessions.

We should consider whether we want to have each multisession clustering run produce a unique .clu file to avoid confusion about what process generated a specific .clu file.