Add list to exclude words from the wordcloud

[rbbeeston]

The word cloud for the release report contains "boostorg". and "org"we would like to exclude them. Considering that, there could be other words in the future that we may want to exclude for one reason or another, so it would be good if there was an easy to update list that could be made for that purpose, we can discuss if it would be just a flat-file or a database entry with an interface