Remove dates from blog markdown file names

[jderochervlk]

The react router plugin for markdown includes the full filename in the url.

We have scripts that transform the names and generate urls stripping out the dates.

We can simplify this by removing it from the file names and making sure it's on the frontmatter.

[fhammerschmidt]

I am all for this, always forgot to move the date in the filename anyways.