showcase: layout skeleton

[catlabs]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Expected behavior

Keep the same look and feel as the AAH
Create the main html of the layout (header, content, menu, footer)
Transform PCSS IN SCSS and adapt the SCSS to work with Angular Material 2