Include .measure results in Analysis with ngspice-shared

[infinitymdm]

Related to #346

This PR allows PySpice to parse .measure results out of ngspice run output and attach them to Analysis objects when using the ngspice-shared simulation backend.

The code changes should be fairly straightforward - just fetch the results of a .meas directive from the response to ngspice run control directives, then pass the measurements up to the Analysis object.

[Kreijstal]

Is this different than #160 ?

[infinitymdm]

Is this different than #160 ?

For starters, this PR only changes about 50 LOC vs the 1000 or so in #160. I just return the .measure results by passing them up the call stack. I'm not entirely sure what they're doing.