Speed up the plotting routines
Description
[Following up on #36 (comment 5293583)]
At the moment, the DAC scans and S-bit rate plotting routines are so slow that they are basically unusable at p5. They may also suffer from memory leaks.
Plotting is currently disabled by default but must be sped up to a reasonable level. Any memory leak should be fixed as well.
Possible fixes
De-couple the analysis from the plotting. A first function can take care of the analysis and a second routine can plot the results if desired. The plotting routine should use a single figure and re-use the axes to speed up the rendering process and avoid memory leaks.