move checkstyle config to dedicated folder
get checkstyle config in line with java-client
added getters for mx status
added method to compute a key
add methods to create entry document with ttl

convert values to Serializable (and only accept Serializable), determine
correct ttl from policy and type of operation, prepare a Serializable
Document.

we will have to find a better way of enforcing Serializable values.
implement get

with statistics and saved as a SerializedDocument
implement getAll and containsKey