Investigate adding delays in continuous projs in Neuron/jLEMS

Likely that it would only be possible in mapping jNeuroML_NEURON in the short/medium term. Longer term source jLEMS could be extended to support this, but also it should be possible to have these delays in a future mapping NeuroML->TVB.

Re NEURON, some info here on implementing delays like this in mod files:
https://www.neuron.yale.edu/phpBB/viewtopic.php?f=16&t=1989
