Modified sorting routine to use secondary key and used this in several places to simplify sorting of LAPW, stars...

...I hope this works. ...at some point we need a clear program logic
for this. Right now it is a nightmare. There are too many different
implicit cases one has to consider.

This is done to make the determination of energy parameters more robust.
It seems to break some tests. But this does not necessarily mean that it
is wrong.

Changed the defaults in atom_input.f and added some timers&stops to prevent this in future.

The preconditioner already improves the convergence of Cu and Fe files, but the starting distance is higher than for the older fleur version and tests run up to test 7 only (does not fail, but hangs).

...in optional/pldngen.f90 this has to be strongly polished.