Add scraper for the list of senators

For each senator, it gets the full name and the Senate ID. It can scrape both the list of current senators or the list of an explicit legislature.
Add MP list URL patterns for Senate

The first URL pattern matches the list of current senators. The second one allows to specify a legislature number in order to get the list of senators that seated during this legislature.
Merge branch 'refs/heads/senate-mp-list-scraper'