Pagegenerators: Add filter for article-bodies

Add a filter that matches a regex against the bodies of all pages.

Original-Change-Id: I8c659479f3591446fbea8b0ac5fde8a72c8a08e4
Change-Id: I90d29e4762bec1f8259dbdd5ef2f2adc9bd578f9
Merge "Pagegenerators: Add filter for article-bodies"