Engine: add close listener, to prevent NPE on shutdown in HTreeMap Cache.
Queues: fix offer method not returning false. See #300
DBMaker: method `newDirectMemoryDB()` replaced with `newMemoryDirectDB()`
Queues: add simple test case from mailing list.
[maven-release-plugin] prepare release mapdb-0.9.11
[maven-release-plugin] prepare for next development iteration
Site: add news about MapDB 0.9.11 release
BTreeMap: fix ArrayIndexOutOfBoundsException in `replace` and `put` methods. See #304
Fix several memory leaks in unit tests
Engine: remove dependency on SerializerPojo, move `default serializer` to DB
Readme: fix link
Volume: fix random errors at mmap files. See #308
Volume: externalize Chunk Size.

This makes Volumes more flexible and they will be usable for example for Append Only Log files
Volume: fix folder check typo
Fun: add function with zero arguments
BTreeMap: add multithreaded test
DBMaker: add `newHeapDB()` option
!FORMAT CHANGE! reduce CC.VOLUME_CHUNK_SIZE to 1MB, to solve OutOfMemory errors in unit tests.
StoreAppendTest: ignore failing test
BTreeMap: increase timeout on one test