Allow renamed channels in simulation

[michaeldeistler]

Previously, we used type(channel).__name__ to determine if a channel already exists in the network.

However, if we rename a channel, we want to consider the channel a new (different) channel with its own parameter names etc. Therefore, we now use channel._name to determine if a channel already exists.

The difference is easily visible when doing:

renamed_hh = HH()
renamed_hh.change_name("NeuronHH")

comp = jx.Compartment()
branch = jx.Branch(comp, nseg=4)

branch.comp(0.0).insert(HH())
branch.insert(renamed_hh)

And then inspecting branch.nodes["HH"]. Before this commit, this returned:

0    True
1    True
2    True
3    True
Name: HH, dtype: bool

Now, it returns:

0    False
1    False
2    False
3     True
Name: HH, dtype: bool

@huangziwei FYI