Remove default num_chan (sparsity) column and add 'clear' label shortcut

[alejoe91]

The sparsity column is redundant and just takes up space.

Also adding the c shortcut to clear labels

[chrishalcrow]

I'm in favor of this, but maybe there's a reason to include the sparsity: @samuelgarcia ??
If there is, maybe we can add it to the columns but turn it off by default?

[alejoe91]

I'm in favor of this, but maybe there's a reason to include the sparsity: @samuelgarcia ?? If there is, maybe we can add it to the columns but turn it off by default?

I'm in favor of this, but maybe there's a reason to include the sparsity: @samuelgarcia ?? If there is, maybe we can add it to the columns but turn it off by default?

Done in last commit: just adding it to the controller.units_table does the trick!

[alejoe91]

@samuelgarcia approved this and he also said we can get rid of num_chan completely (which is honestly a bit useless :P)