Pack iDMRG and fDMRG steps, deal with boundary

Pack iDMRG and fDMRG steps to subroutines, clear up the kernel, add a
show DMRG status routine to print data. By branching according to L in
fDMRG, the boundary issue has been handled. The boundary tensor is
restarted under each sweep, such that spontaneous symmetry broken can
take place.