Cherry-picked actions.py and tests from features/rengine branch.
Fixed bug in SseHTTPServer (wrong error message in case message is not a dict), adapted tweetprocessor and queuefiller to Jan's wrapper class.
Added links to generated docs to index.html.
Merge branch 'develop' into feature/wordcloudgadget
Added wordcloud actions at the Python side, created event handlers on the Javascript side.