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* added: support for options on MongoAdapter - keyword options will be chained
to the cursor returned by the initial `Base.find()` call, using the key as
the method name, and the value as the argument.
* fix: Overhauled `Baseevict()`. `Base` now has a class method
`Base.evict_document()` that actually performs the work of removing a
document from the cache backend. The instance method `Baseevict()` has been
modified to perform eviction using every resource for which a query can be
generated (via `Resourcegenerate_query()`). Documents that may have been
stored by association are also removed from the cache. Noteably, in a
parent-children relationship using an aggregate association, calling
`child.evict()` will not clear parent.children from the cache, because all of
the children are stored in the cache as a single document when an aggregate
association is used, and the child does not have a handle to that document.
* added: "eviction" hooks - before_eviction, et al.