Implement mixable_holder::clear_each_mixables
Add clear() to server_base
Modify result type of server_base::clear
Add clear to clustering
Regenerate
Increment revision when clear
Add test for clear
Add clear_mine for clustering::storage
Clear gmm state when empty data is passed in gmm::batch
Clear k-means when empty data is passed
Add test for clearing clustering
Output log when clear
Merge pull request #744 from gintenlabo/implement-clear-for-clustering

Implement clear for clustering (#579)