MaterialDesign: Add row hover and move cpuload icon

[TrimmingFool]

Unlike the other StatusBar entries, the cpuload plugin used a div instead of a table element. This is an old issue which resulted in the material design theme looking like this:

Now, it looks like this:

Additionally, I rounded the progress-bar and added a hover styling, inspired by the club-QuickBox theme.

[stickz]

Thanks!