Allow to configure the TODO-like words to scan for / display

[sschuberth]

We have some test assets in our code case that use (the rather offensive) WTF keyword, and we'd like to either

a) not scan for WTF in the first place, or
b) have a way to filter the web view for only those TODO keywords used by us (and also only take those keywords into account in the count of TODOs).

Or is there already a way to achieve this?