leshan-0.1.11-M12

Build artifacts are available on maven central.

Change logs:
b0aaf04 - Bumping nexus-staging-maven-plugin to version 1.6.7
11e7580 - Disable autoReleaseAfterClose when deploying to Nexus
3dd7873 - Code review clean-up
1552b4e - Use encoder/decoder to know if a content format is supported.
ad24783 - Add Timestamped Data support on Observation
6c046c2 - Add Timestamped Data support on LwM2mNodeEncoder/Decoder
3a6eba8 - remove generics
967614f - Add Timestamped Data support on LwM2mNodeJsonEncoder
243a8a0 - Change Time attribute of JsonArrayEntry from Integer to Long.
3608b3b - Add Timestamped Data support on LwM2mNodeJsonDecoder
25e1b55 - Define interface for encoder/decoder
f9b422f - move from static LwM2mNode encoder/decoder to dynamic one
3340178 - Change ContentFormat from enum to class to prepare extensibility
b91f346 - Add cluster support for QueueMode
aeb7586 - Add new send API (async with ticket)
9479dde - Add a Redis "Registration" event publisher
ab1be1b - Remove mokito test dependency
32fd096 - switch log4j2 to test deps