Read props from typescript files

In order to get the props we are using [react-docgen](https://github.com/reactjs/react-docgen), which in theory should work with typescript:
> If you are using flow or typescript then react-docgen can also extract the type annotations.

In reality, parsing FlexLayout [Layout.tsx](https://github.com/openworm/geppetto-client/blob/splitRefactoring/geppetto-ui/src/components/flex-layout/src/view/Layout.tsx) currently is not working with an error occurring at [this line](https://github.com/MetaCell/geppetto-website/blob/development/geppetto-showcase/components/showcase/ShowcaseUtils.js#L75).

In order to surpass this problem a dummy js file called [FlexLayoyt.Layout.js](https://github.com/openworm/geppetto-client/blob/feature/252/geppetto-ui/src/components/flex-layout/showcase/FlexLayout.Layout.js) was created to define the proptypes in a standard react/javascript format.

Ideally that would not be necessary, and that's the reason of this card.

Depends on #2

Start at components/showcase/ShowcaseUtils.js line 75 and inspect how it invokes react-docgen for geppetto-ui/src/components/flex-layout/src/view/Layout.tsx. Compare the workaround in geppetto-ui/src/components/flex-layout/showcase/FlexLayout.Layout.js, accounting for the dependency on issue #2. Done means Layout.tsx can be parsed for props without the dummy JavaScript file.

Written by the indexing model from the issue text.