using a ThreadLocal in order to maintain 1 instance of ObjectMapper per Thread, instead of 1 instance for the whole StdCouchDbConnector. This greatly reduces contention on ObjectMapper internal state synchronization when multiple thread are using it at the same time, which is often the case in a server side application.
just a refactoring : moved Attachment related stuffs to new class StdAttachmentCouchDbConnector. Existing methods now just delegates to it.
extended AttachmentCouchDbConnector in order to support Apache HttpEntity, providing a way for user applications to save an Object directly in a streamed way without relying on temporary ByteArrayOutputStream+ByteArrayInputStream, just by implementing an appropriate HttpEntity
Merge branch 'ReducingThreadSynchronizationContentionInsideObjectMapper' into integration
Merge branch 'ExtendingAttachmentsSupport' into integration

Conflicts:
	org.ektorp/src/main/java/org/ektorp/impl/StdCouchDbConnector.java