Add support to record other variables in LEMS
It would be great to be able to save otehr variables beside v as specified in the LEMS file, e.g.
<OutputFile id="of1" fileName="hh_forJupyterNotebook.dat">
<OutputColumn id="v" quantity="hhpop[0]/v"/>
<OutputColumn id="m" quantity="hhpop[0]/bioPhys1/membraneProperties/naChans/naChan/m/q"/>
<OutputColumn id="h" quantity="hhpop[0]/bioPhys1/membraneProperties/naChans/naChan/h/q"/>
<OutputColumn id="n" quantity="hhpop[0]/bioPhys1/membraneProperties/kChans/kChan/n/q"/>
<OutputColumn id="I_na" quantity="hhpop[0]/bioPhys1/membraneProperties/naChans/iDensity"/>
<OutputColumn id="I_k" quantity="hhpop[0]/bioPhys1/membraneProperties/kChans/iDensity"/>
<OutputColumn id="I_l" quantity="hhpop[0]/bioPhys1/membraneProperties/leak/iDensity"/>
<OutputColumn id="I_inj1" quantity="hhpop[0]/pulseGen1/i"/>
<OutputColumn id="I_inj2" quantity="hhpop[0]/pulseGen2/i"/>
</OutputFile>
at https://github.com/openworm/hodgkin_huxley_tutorial/blob/master/Tutorial/Source/LEMS_HH_Simulation.xml. Currently fails e.g. see https://github.com/openworm/hodgkin_huxley_tutorial/actions/runs/3438827344/jobs/5735390798