Clip PCA bar chart maxima

[leesharkey]

Changing the scale of the bar chart for every sample complicates interpretation.

Fortunately,

• It seems that values for PCs that exceed +/- 6 are very rare and therefore don't carry much information
• They only happen often in PC0, which is not a very important PC for interpretation
• In the other PC dims they're often pathological (e.g. when the level is finished but the hx keeps changing 'in the dark')

It would therefore be nice if the bar chart kept a constant scale that used +/- 6 as its maximal values.

[NixGD]

Changed default behaviour to [-6, 6]. To alter behaviour for a specific panel, you can pass in barChartOptions: {ylims: [min, max]} or barChartOptions: {ylims: null} for autoscaling.