MLT Query: Support for ignore docs

Adds a `unlike` parameter to the MLT Query, which simply tells the algorithm
to skip all the terms from the given documents. This could be useful in order
to better guide nearest neighbor search by telling the algorithm to never
explore the space spanned by the given `unlike` docs. In essence we are
interested about the characteristic of a given item, but not of the ones
provided by `unlike`, thereby forcing the algorithm to go deeper in its
selection of terms. Note that this is different than simply performing a must
not boolean query on the unliked items. The syntax is exactly the same as the
`like` parameter.
My question is just what is the rule we should apply whoever the developper or whatever the IDE. 
Sounds like it's not super clear to me: https://github.com/elasticsearch/elasticsearch/blob/master/CONTRIBUTING.md#contributing-to-the-elasticsearch-codebase

> Don't worry too much about imports. Try not to change the order but don't worry about fighting your IDE to stop it from switching from * imports to specific imports or from specific to * imports.