Fix detailed plots collapsing on y-axis.

[namikk]

Detailed plots that contain a legend (blas3, copy & vector) get their y-axis collapsed when the following things occur:
Step 1: do a benchmark run and have the results displayed on their respective detailed plot
Step 2: do another benchmark run while deselecting one of the benchmarks from the previous run
Step 3: detailed plots of deselected benchmarks now have their y-axis collapsed
The easiest way of reproducing this bug is to first run all benchmarks, then deselect some of the problematic benchmarks (blas3, copy & vector) and observe how their plots get messed up when other benchmarks are executed. (see attached screenshot)
I was unable to pinpoint the source of the problem, but it seems that something goes wrong with the detailed plot layout when it has a legend attached to it. Probably something to do with the way plot legends are initialized over multiple result plotting runs.