Add Barrier for QumodeCircuit

[Hugh-888]

1. Add barrier for qumode circuit

nmode = 4
cir = dq.QumodeCircuit(nmode=nmode, backend='fock', init_state='vac')
for i in range(nmode-1):
    cir.bs([i, i+1])
    cir.ps(i)
    cir.barrier()
for i in range(nmode-2):
    cir.bs([i, i+1])
    cir.ps(i)
    cir.barrier([i, i+1, i+2])
for i in range(nmode-1):
    cir.bs([i, i+1])
    cir.ps(i)
    cir.barrier([i, i+1])
cir.draw()

2. Fix bug for Fail to draw circuit if adding more gates to unrolled global circuit #107

backend = 'fock'
cir = dq.QumodeCircuit(nmode=nmode, backend=backend, init_state='vac', cutoff=2)
for i in range(nmode):
   cir.delay(i)
for i in range(nmode-1):
   cir.bs([i, i+1])
for i in range(nmode):
   cir.delay(i)
cir.homodyne_x(0)
cir.draw()

global_cir = cir.global_circuit(nstep=2)
global_cir.draw()

for i in range(global_cir.nmode-1):
    global_cir.ps(i)
global_cir.draw()

[sansiro77]

_draw_nstep相关的没删