Eliminate dependence on tvmet

Use Eigen instead.  Note that Eigen uses column-major storage by
default whereas tvmet offers only row-major.  Therefore one can pass
an Eigen matrix to a fortran subroutine as a 2D array without
transposition.
Make existence of Mathematica mandatory
Make existence of lapack and BOOST multithreading mandatory if
the use has chosen to use the latice method.
Merge branch 'master' of ssh://pktlogin.phy.tu-dresden.de/soft/users/theory/FlexibleSUSY
Correct error output message: GSL is also needed of the two_scale
method
Eliminate dependence on boost vector

Replace boost vectors by eigen arrays in src/rk.[ch]pp
Do not overwrite other options if the user asks for the program
version.
Merge branch 'master' of ssh://pktlogin.phy.tu-dresden.de/soft/users/theory/FlexibleSUSY
Isolate old Runge-Kutta routines with DoubleVector interface

Move them from numerics.h into liblegacy
Hide from numerics.h: DoubleVector dd(double x, const DoubleVector& y);
Link legacy library to test programs that depend on it.
Optimization: Do not calculate b22 twice.
I checked that the resuts in `ans' and `answer' are identical (using
assert() an running examples/softsusy.x and the tests).
Store only a const version of the model in the error class, in order
to allow const functions to throw errors.
Check for tachyons in loop mass calculation functions, too.
Allow the user to overwrite the maximum number of iterations.
The default value is still determined from the accuracy goal.
Bugfix: all algorithms depend on the new rk.h/cpp module
Add test program for legacy and Eigen based Runge-Kutta algorithm.
Add beta function base class, which uses the Eigen-based Runge-Kutta
algorithm.  It is inspired by Softsusy's RGE class.
Beautify the Runge-Kutta routine a little bit more

Use more Eigen builtins that could also lead to a potential
optimization
Set default running precision to the value used in Softsusy
Add test program for the new Beta_function class