Add string normalisation to the base plugin class.
Add string normalisation to the base plugin class.

simple_extract() in the base plugin class now:
1/ strips the HTML tags
2/ strips all characters except the latin letters and digits + the ' '
blank space character, ASCII 0x20
3/ normalises all remaining whitespace, replacing multiple whitespace
characters with the ' ' blank space char
4/ lowercases the string

These operations are applied to both the incoming page source and the
license statement which we're looking for in that page's source.

CottageLabs/OpenArticleGauge,CottageLabs/OpenArticleGauge,CottageLabs/OpenArticleGauge