DATAMONGO-354 - Update.pushAll(…) now supports multiple values.

Update.pushAll(…) now is a multiFieldOperation which allows to send values for different fields within one command.

Original Pull Request: #122.
DATAMONGO-848 - Added tweaks to be compatible with Java driver 2.12.

Added build profile to be able to build against next Mongo Java driver version (2.12.0-rc0) currently. Tweaked Bundlor version replacements to allow binding non-OSGi compatible Mongo driver versions.

Exception translator now handles newly introduced MongoServerSelectionException which the driver throws to indicate it can't connect to a MongoDB instance as of driver version 2.12. GridFsTemplate now uses an empty query object instead of null to indicate that no query should be used. 

Adapted test cases to be able to deal with the slightly changed representation of serverUsed in command results (2.12 removed leading slash).