FIXED: Steady state solver uses umfpack by default

This was turned off in the past due to an error in an earlier library.
UPDATED: iterative stead-state solver now uses spilu preconditioner

Use sparse incomplete LU preconditioner for steady state solver.
Method is now stablized bi-conjugate gradient so that we do not need to
calculate dagger of preconditioner.
made energy-level diagram graph's fig and axes as optional arguments
FIXED: Norm not conserved using func-based time-dependence in mcsolve

Underlying data array was being multiplied TWICE by -1.0j.
ADDED: Created DIA sparse matrix-vector product

Since most Hamiltonians and Louvillians are banded matricies, taking
the spmv in DIA format may be faster.  Still need to check.
FIXED: mcsolve no longer prints est. time for a single-trajectory
FIXED: About box stylesheet not found

Somehow the name of the button stylesheet had been changed.
manual merge of upstream master changes into win-support branch