Enable a SIESTA function for each of the classes

[zerothi]

Instead of having the excessive code examples much of it may be reduced to a single SIESTA function which does everything.

I.e. the examples should be shortened and input into each of the classes such that one may do:

relaxation = flos.LBFGS(...)
-- Pass the siesta table for interaction
-- and retrieve the function that is going to be used
-- to communicate with SIESTA
siesta_comm = relaxation:SIESTA(siesta)

Thus the use of flos may be greatly eased for those who are willing to use the respectable defaults.

Although this heavily limits the fine-tuning of the method, it will greatly improve usability