Generalized persistence querying (with delete) - sketch.
* Query is now an interface
* There are multiple types of queries
* A Query is replied to with QueryAnswer, which may or may not carry data
* Deleting queries are supported

relates to #116
relates to #118
relates to #119
Merge branch 'master' of github.com:radek-macha/everBeen
Fix abstract query serialization (Jackson)

relates to #116
relates to #118
relates to #119
Polymorphic serialization/deserialization support for Query and QueryAnswer. Minor fixes.
* generalize persistence layer querying to Query and QueryAnswer
* create QuerySerializer for their serialization/deserialization
* JSON mappings are hidden in skeletal abstract implementations of Query/QueryAnswer and are used in QuerySerializer and QueryChecks to prevent JSON mappings from leaking to API
* randomize 0MQ port selection (was causing problems during re-binding, sometimes made queue tests fail)

relates to #116
relates to #118
relates to #119
Merge branch 'master' of github.com:radek-macha/everBeen