Capped collections

[Ivshti]

LinvoDB needs to support capped collections, like MongoDB

With the events system, this shouldn't be too hard to implement as an add-on module. The logic will be:

1. when new documents are inserted (listen to the inserted event
2. lookup an index we'll be capping on directly (.indexes[idxName]. ...) - e.g. an index by mtime or ctime
3. take the documents of this index which are not in the first N (cap size) and remove them with Doc.remove()

[Danielv123]

Capped collections would be a great addition.