Remove unused data/ directory (#712)

* Remove data/ directory, contents as they are not used now in Arbor.

data/hh.mod

-TITLE hh.mod   squid sodium, potassium, and leak channels
-
-: COMMENT
-:  This is the original Hodgkin-Huxley treatment for the set of sodium, 
-:   potassium, and leakage channels found in the squid giant axon membrane.
-:   ("A quantitative description of membrane current and its application 
-:   conduction and excitation in nerve" J.Physiol. (Lond.) 117:500-544 (1952).)
-:  Membrane voltage is in absolute mV and has been reversed in polarity
-:   from the original HH convention and shifted to reflect a resting potential
-:   of -65 mV.
-:  Remember to set celsius=6.3 (or whatever) in your HOC file.
-:  See squid.hoc for an example of a simulation using this model.
-:  SW Jaslove  6 March, 1992
-: ENDCOMMENT
-
-UNITS {
-    (mA) = (milliamp)
-    (mV) = (millivolt)
-    (S) = (siemens)
-}
-
-NEURON {
-    SUFFIX hh
-    USEION na READ ena WRITE ina
-    USEION k READ ek WRITE ik
-    NONSPECIFIC_CURRENT il
-    RANGE gnabar, gkbar, gl, el, gna, gk
-    GLOBAL minf, hinf, ninf, mtau, htau, ntau
-}
-
-PARAMETER {
-    gnabar = .12 (S/cm2)  : <0,1e9>
-    gkbar = .036 (S/cm2)  : <0,1e9>
-    gl = .0003 (S/cm2)    : <0,1e9>
-    el = -54.3 (mV)
-    celsius = 37 (degC)
-}
-
-STATE {
-    m h n
-}
-
-ASSIGNED {
-    v (mV)
-
-    gna (S/cm2)
-    gk (S/cm2)
-    minf
-    hinf
-    ninf
-    mtau (ms)
-    htau (ms)
-    ntau (ms)
-}
-
-BREAKPOINT {
-    SOLVE states METHOD cnexp
-    gna = gnabar*m*m*m*h
-    ina = gna*(v - ena)
-    gk = gkbar*n*n*n*n
-    ik = gk*(v - ek)
-    il = gl*(v - el)
-}
-
-INITIAL {
-    rates(v)
-    m = minf
-    h = hinf
-    n = ninf
-}
-
-DERIVATIVE states {
-    rates(v)
-    m' =  (minf-m)/mtau
-    h' = (hinf-h)/htau
-    n' = (ninf-n)/ntau
-}
-
-PROCEDURE rates(v) :(mV))
-{
-    LOCAL  alpha, beta, sum, q10
-
-    q10 = 3^((celsius - 6.3)/10)
-
-    :"m" sodium activation system
-    alpha = .1 * vtrap(-(v+40),10)
-    beta =  4 * exp(-(v+65)/18)
-    sum = alpha + beta
-    mtau = 1/(q10*sum)
-    minf = alpha/sum
-
-    :"h" sodium inactivation system
-    alpha = .07 * exp(-(v+65)/20)
-    beta = 1 / (exp(-(v+35)/10) + 1)
-    sum = alpha + beta
-    htau = 1/(q10*sum)
-    hinf = alpha/sum
-
-    :"n" potassium activation system
-    alpha = .01*vtrap(-(v+55),10)
-    beta = .125*exp(-(v+65)/80)
-    sum = alpha + beta
-    ntau = 1/(q10*sum)
-    ninf = alpha/sum
-}
-
-FUNCTION vtrap(x,y) {
-    : Traps for 0 in denominator of rate eqns.
-
-    : Disabled for function inlining...
-    : there is a very good case for making vtrap a builtin function for the language
-    : - it is ubiquitous: used in so many models of ion channels
-    : - platform specific optimizations written in assembly/intrinsics
-    :   required to facilitate vectorization/minimize branch misses
-
-    :if (fabs(x/y) < 1e-6) {
-    :    vtrap = y*(1 - x/y/2)
-    :}else{
-    :    vtrap = x/(exp(x/y) - 1)
-    :}
-
-    vtrap = x/(exp(x/y) - 1)
-}
-

data/passive.mod

-TITLE passive membrane channel
-
-UNITS {
-    (mV) = (millivolt)
-    (mA) = (milliamp)
-    (S) = (siemens)
-}
-
-NEURON {
-    SUFFIX pas
-    NONSPECIFIC_CURRENT i
-    RANGE g, e
-}
-
-INITIAL {}
-
-PARAMETER {
-    g = .001    (S/cm2) :<0,1e9>
-    e = -70 (mV)
-}
-
-ASSIGNED {
-    v (mV)
-}
-
-BREAKPOINT {
-    i = g*(v - e)
-}