multisearch: bugfix release

Just released a bugfix release of my multisearch Weka package. C├íssio reported a weird threading issue, which stemmed from the executor pools not shutting down properly in case of a failed search (e.g., abnormal state – all cached). The new release now guarantees that the clean-up code gets called, no matter what. In case of the multi-threaded search, the executor pool now gets shutdown properly.