Design guidelines - links contrast

In Studio some areas are missing contrast

• In modeler help tooltips (see 2017-12-11-links-missing-contrast.png) almost no contrast
• In modeler automatic registries links lack contrast too (see 2017-12-11-registries-links.webm)

Devs will need indications about color scheme to apply in these conditions

TODO

• Provide dev applicable guidelines for the areas missing contrast in Studio