leshan-0.1.11-M13

Build artifacts are available on maven central.

Change logs:
f1982ed - Fix LwM2mSingleResource generic constructor.
18d3271 - Replaced Exceptions with BootstrapFailureCause
387bee8 - Added notification of early failure
cd0018f - Hides security-related values from toString() (#179)
58c87fc - Replace int[2] by ObjectLink class
b4fb4ba - Support objlnk for TLV and Text format.
e458b07 - Add project specific: organize import + format on edited line only.
5615cbc - Add Context for observation
51d4ed3 - QueueModeTest clean-up (typo+remove unused method)
a3fdd02 - Change log config for integration tests (off => error)
fb52c95 - use Californium 2.0.0M2
aa764a9 - #168: fixed duplicate observations for the same resource path.
a8df823 - #160: fix QueuedRequestSender race condition
1a68fd3 - fix potential NPE in QueueModeObservationRegistryListener newValue()
89a52c2 - changed clientEndpoint to Client in ResponseListener as described issues #165
947ead6 - Fix fix NPE in BootstrapSecurityStore of bsserver-demo again ...
ddaa6e4 - fixed check-then-act situation in InMemoryMessageStore
cd6738c - Introduced cancelAllPendingMessages in LwM2mRequestSender interface.
efcc708 - enhance content format handling
6081674 - fix NPE in BootstrapSecurityStore of bsserver-demo
defadcf - #155: fix format selection of leshan-server-demo UI
020e3e0 - add toString() equals() method to ContentFormat.
86295f9 - ContentFormat is now mandatory. (remove magic to compute default value