Add \ncds to do the same as \cds without wire.

[ElieGouzien]

As described in the title, it adds a command (\ncds) to do the same as \nds but without wire.

An example is included in the commit (in the documentation).
Another example is:

\Qcircuit @C=1em @R=.7em {
	& \gate{\phi} & \qw & \ncds{1}{=} & & \ctrl{1}   & \qw \\
	& \ctrl{-1}   & \qw &	          & &\gate{\phi} & \qw
}

Since I don't understand everything in the code I've written, I encourage you to carefully read it.