Get groups & committees the senator is related to
Fix type of return value in docblock
Tweak comment
Get the birthdate of senators
Create ScrapingHelpersTrait

Create a trait to store helper methods for scraping operations. Move helper methods from the main abstract scraper to the trait and make the scraper use the trait.
Extract extractDate() to ScrapingHelpersTrait

This allows to remove this method and the related property from two individual scrapers.
Merge branch 'scraping-helpers-trait'
Get the gender of senators
Alphabetically order results of MP scrapers

Make the MP and MPList scrapers return arrays with keys that are alphabetically ordered.
Fix spacing