Toolbar: hover highlighting too intense

[bill]

• Problem: style of hover background colour and an outline is visually too much/not cohesive with the rest of the tundra theme:

• Recommendation: Lighten both the background and border colour for the hover state:

.tundra .dijitToolbar .dijitDropDownButtonHover {
	border: 1px solid #869cbf;
	background-color:#e1e5f0;
}

Taken from ​IBM Design Leadership recommendations.

[bill]

(In [13434]) Make toolbar hover highlighting less intense for tundra (fixes #6504).