Updated colours Ghost buttons

[ulde01]

(Moved from https://github.sebank.se/DesignLibrary/AngularComponents/issues/57)

Design change 2019-02-13

The Ghost button is updated to two versions:

Ghost button light

• Transparent with a "White" outline (1 px).
• On hover: Background and outline is "Grey 2".

Ghost button dark

• Transparent with a "Grey 2" outline (1 px)
• On hover: Background and outline is "White".

Reason: The instruction for the Ghost button is clarified. It is used on coloured background and photographs. Ghost light is for darker backgrounds, and Ghost dark for lighter backgrounds.

Discussion: https://github.com/sebgroup/design-library/issues/35

Design Library description: http://designlibrary.sebank.se/components/forms/button/#usage

Thank you! /Ulrika Design management

[hjalmers]

see https://github.com/sebgroup/ng-components/issues/18#issuecomment-478984462