ui: table implement footer

[nicanac]

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

Current behavior

Actually, there's no table summering a column in a footer available for the developers.

Expected behavior

As it's available in angular material, we could simply add it to stark.
Angular Material: https://material.angular.io/components/table/examples
Example: https://stackblitz.com/angular/yarvnglavmk?file=src%2Fapp%2Ftable-footer-row-example.ts