We've changed the way plugins are activated, and removed the notion of
deactivated plugins.
Now plugins activate asynchronously.
When calling a plugin, it will be activated if it wasn't, and the call will wait
for the plugin to be fully activated.
This lines up the names in the conversion plugins with the [emotionML suggested vocab](https://www.w3.org/TR/emotion-voc/#dimensions).
emoml has different names for the 4-dimensional fsre scheme and the 3-dimensional vad scheme, which this pull request has added.
I've added the "unpredictability" dimension and mapped big6:surprise to it's maximum value. The assumption is that surprise varies between 5 and 10 to be in line with the other dimensions (no such thing as negative surprise, so no values less than 5). I see that arousal also has all values >5 (so no negative arousal). Ideally, surprise mappings for V, A and D should be calculated empirically - I think there'll be some arousal and possibly slightly lowered dominance.
I wonder if we should use another colon in the emoml names, eg: "emoml:fsredim:valence" or "emoml:big6:happiness", since the [emoml suggested vocab](https://www.w3.org/TR/emotion-voc/xml) only specifies names like "happiness" in a category "big6" (ie: it's hard to know which is the category in "big6happiness").
We'd have to go through the example plugins and make sure they also conform...
open to discussion on this btw...
ps: apologies for multiple changes in this one pr..
Using this server in production is discouraged, but to implement a
proper asynchronous server with tornado/gevent every blocking call would
have to be converted to a non-blocking call.
Failing to do so causes deadlocks like senpy/senpy#35
For now, it is easier to just use the default server.
I've used euclidean metric instead of taxicab as I feel it makes more sense (taxicab has bizzare unintuitive effects for points far from the centroids).
