Standardise hover behaviour

[bia]

Throughout Weave Cloud, buttons often hover like hoverBackground: darken(0.05, colors.somecolor) and text links generally lighten.

Outside of that, there are quite a few random opacity changes happening throughout.

Now that button backgrounds are generally becoming darker for AA compliance with white text, we might want to consider lightening on hover instead.

Anyways, we should do a pass of noting all of these different behaviours and grouping them, just as the colors. It would be a fairly easy win.

[bia]

Here's an overview of the 7 different hover styles existing in our app :

Style		Before	After	Change
	Background	purple25	purple100	darken
	Text	purple800	purple900	darken
	Background	purple25	white	lighten
	Text	black	blue700	lighten
	Background	purple50	-	none
	Text	purple400	purple900	darken
	Background	purple25	purple100	darken
	Text	purple900	-	none
	Background	white	gray50	darken
	Text	purple900	-	none
	Background	purple25	-	none
	Text	gray600	80% opacity	lighten
	Background	purple700	purple400	lighten
	Text	white	-	none
	Background	purple25, close dropshadow	purple25, far dropshadow	none
	Text	blue700	-	none

To summarise the color changes on hover,

	lighten	darken	none
Background	2	3	3
Text	2	2	4

[bia]

Apart from existing hover behaviours, the expansion triangle of deployment images and the top Resources/History tabs are in need of hover behaviour to make them more discoverable and to match the style of the existing app. They could look like

Existing	On hover