investigate `cell-permute`

[cattabiani]

While working on this: #337 I noticed that cell-permute is a coreneuron setup that changes the memory layout. It can have 3 values:

• 0: AoS
• 1: SoA (gpu, cpu)
• 2: SoA (gpu only)

at the moment the value is hardcoded to 0 in default_cell_permute. 2 facts:

• I tried to change this value in some tests but, in initial analysis, the value was not correctly propagated to coreneuron. I suspect this feature was only partially implemented
• the new report.conf and coreneuron reports are not tested, currently, with this value different from 0

We should test, investigate, and profile this since it can provide computational speed-up (and lower costs) even if only for value 1 since we do not have gpus atm

EDIT: cell-permute for coreneuron reports was fixed in this pr: neuronsimulator/nrn#3587

We need to allow setting cell-permute from neurodamus. New issues to better track that

[cattabiani]

@jplanasc @jamesgking @WeinaJi @juanjosegarcan @mgeplf

just to give you a heads-up on a possible vector of attack to improve performance. I think it is worth at least exploring if we can indeed use it