Support filtering of state listings

[DanielJanzon]

Today, with msg state <label> [left|right N] you can get a very long listing like

P(|000000>) = 0.0000
...
P(|110110>) = 0.0000
P(|110111>) = 0.0000
P(|111000>) = 0.0078
P(|111001>) = 0.0000
...
P(|111100>) = 0.0000
P(|111101>) = 0.0000
P(|111110>) = 0.0000

Perhaps it would be helpful to be able to filter this output. Some examples

msg state iteration1 left 6 filter pattern xxxxx0  ; filter any state with last bit 0 
msg state iteration1 filter filter zero-prob  ; filter any state that has zero coefficient
msg state iteration 1 filter right 7 filter zzzxxx  ; filter any state where any of z bits is non-zero

[odanielson]

I think this make sense, but maybe good to use levels instead of keywords, like filter prob > 0.3
It would also make sense to be able to specify specific qubits, like msg state iteration qubits 3-7,11