Implemented new ODE solver class METAN_A

  This (fast) ODE solver for non-stiff problems comes with a
  simple linear interpolation scheme, for the time being...
Minor changes (mostly typos and legibility)
Added an Expression Parser Object

  Now, expression can also be build from strings such as Python expressions.

  Secondly, an update of the cbp2make Makefile was overdue. Should be fixed
  by this commit.
Added math function pow(a,b) to Parser class

  Enabling math functions with multiple arguments by
  introducing the CommaType in the class Parser.
Added UnaryMinus (and U/Plus) Ops to Parser class
Fixed some issues with UnaryMinus in Parser class
Tried to introduce a third rhs_type in BioSystem.

  Skipped it, since it did not work out so far...
Added a class BioMedication (enabling drug adm)

  Drug release with a concentration 'Dose' is modelled by a
  Gamma distribution,

     y_adm' = Dose * beta^2 * t * exp( -beta*t ) - clRate * y_adm

  hence the parameter alpha = 2 of the Gamma distribution is fixed,
  and the clearance rate is given by 'clRate'.  The parameter 'beta'
  can be used to model specific pharmacokinetic properties of the
  applied drug.
Missed important impl. step of class BioMedication

  Now, the medication is indeed really applied to the ODE system...
  Additionally, corrected the ODE index by 1 (index 0 is reserved
  for the time 't' component!)
Added getErrorMessage(rc) to ODESolver classes

  In order to have a more talkative interface for the user...
Added Hplus(...) and Hminus(...) to class Parser

  A Q-&-D 'solution' for a function definition option,
  as declared in the SBML specs...

  Hplus() and Hminus() are the so-called Hill functions:
  With z := (x/s)**n , we have

        H+ := z / (1 + z) ,  and    H- := 1 / (1 + z) ,

  respectively.  These are sigmoidal, i.e. S-shaped, functions.
Fixed a glitch in BioProcessor::prepDetailedSens.

  When using the Variational Equation for sensitivity computing,
  the wrong dimension of the solution trajectories was checked
  (missing to count the 'virtual' time variable...)

  Additionally, a minor bug had caused some compilation warnings,
  as the 'new' BioMedication class was not included yet in the
  swig interface.  Silly me!

  Finally, bumped the PARKINcpp lib version to 2.1.9 by this commit.
... forgot to *really* add the class BioMedication

  No comment! (...worst things happen at sea, ye'know...)
Bumped addpkg dlib version to 18.9 (most recent)

  Indicated by a switch from Ubuntu 12.04 (precise) to 14.04 (trusty)...
Tiny addendum to previous push just before

  ... included 'dlib/all/source.cpp' again in all targets in the .cbp file.
Revised BioProcessor::prepareDetailedSensitivities

  Detailed sensitivity computation, esp. subcondition calculation,
  now depends consistently on condMax as in the identify method,
  via the system tolerance (xtol/ptol/...) given by calling
  BioSystem::setSystemTol(tol).
system: Add BioSystemODE.cpp and BioSystemVAR.cpp to CMake
addpkg/Ode: Replace non-standard malloc.h by stdlib.h