Add options to hide certain UI elements

[davidanthoff]

I plan to wrap lyra in an electron window and expose that for interactive work in Julia (in the same way that DataVoyager.jl exposes voyager for Julia).

There are a couple of UI things that ideally I would like to tweak:

• Remove the + New button in the Data Pipelines section (because data would be added via Julia code)
• Remove the open and save button
• Possibly remove the export button

There are probably other things that I'm missing right now.