Feature/206

[afonsobspinto]

Closes #195 #197 #202 #206
Contains:

• The geppetto structural split (client, ui, showcase)
• Showcase for BigImageViewer and Connectivity components, following the enhanced showcase template. See lunpark-dev#Geppetto-Showcase for additional information.
• Basic showcase for Plot, FlexLayout, MoviePlayer, GraphVisualizer, ListViewer and Menu (all should be 'easily' updatable to the new structure).

Some notes already discussed but will not be on this PR (unless said otherwise):

• Change plot component to use only instances instead of full model
• Python console, show an image (for now)
• Improve showcase UI/UX ( add material paper, add button to copy source code, others...)
• Add toolbar common component
• Do not set the height -> use flex instead

Originally posted by @filippomc in #198:
Those geppetto-client/geppetto-client scare me. If someone looks at it without knowing the history easily thinks thinks it's a bad copy/paste to fix. Also we should remove direct references to files being inside node_modules. If we don't do that, we need to include the node_modules folder in every deployment. @tarelli I think that getting rid of those references may be one of the next refactorings.

[filippomc]

Thanks @afonsobspinto, added a few minor comments

[afonsobspinto]

Hello @filippomc, I think I addressed all of the minor comments you have added. Please let me know if you want anything else to be changed.

[filippomc]

Thanks @afonsobspinto, this is great stuff.