Design system: the navbar

[christophsax]

Rewrites the spec's navbar section and its drawing on the design system page:

• Left: the blockr mark (also the busy indicator), the workflow's name with a chevron that opens the workflow switcher, and Save with a chevron that opens the save menu (Save, Save as new workflow, Download, versions). No save state as text.
• Right: the view menu, a rule, help, board options, the account avatar.
• A board option "Show views as tabs" puts the views on a second line as tabs.

This is where I want the navbar to go. The code is on feat/navbar-views branches in blockr.dock and blockr.session, which are not pushed yet.

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