Improvements to full game analysis bar

[ksthicke]

1. Make the bar at the bottom so that it only shows from -4 to +4 or something like that (editable in settings). Make sure mate-in-n plots properly too.
2. Make it so that the width of the graph is set to the number of moves before the plotting starts. This way the graph isn't constantly shifting to the left as it readjusts itself.

[ksthicke]

For 2: Want to change this.chartOptions.xaxis.max in evaluateHistory of EvalPlot.vue in a reactive way so that it sets to the total number of moves before it starts updating.