Add more Razor::Matcher operators

This adds a couple more operators to `Razor::Matcher` for processing numeric values. In addition to greater-than, less-than, and their -or-equal counterparts, this adds a `"num"` operator to convert values into their numeric equivalents, if any, or 0 if not.

These had been mentioned on the wiki as useful to have; let me know if there are any other that could be added here.