[Taler] refactoring suggestion

[fabian . kirsch]

Dear all,

take a look at "refresh" for the case of kappa=1.
A lot of variables are then only calculated but never used.
T, K, E may be left out.

writing down the remaining algorithm (without unneccessary computations)
you end up with the equivalent of "second-half-of-withdrawel".

I therefor suggest rewriting withdrawel as:
1.) send money with Wp
2.) get S_K(Wp) as named coin
3.) refresh it if you like, some mints may allow kappa=1 for refreshing 
named coins

greetings Fabian