[cooja] Memory: Added get/setByteArray functions to Memory access class

Provides a cleaner interface to access memory as VarMemory already
contains variable name based get/setByteArray functions.
[cooja] Memory: Added add/removeMemoryMonitor functions

Provides a cleaner interface to access memory as VarMemory already
contains variable name based add/removeVarMonitor functions.
[cooja] interfaces/IPAddress: Indention cleanup
[cooja] interfaces/IPAddress: Added @Override annotations
[ccoja] Added new IPUtils class

Utility class to convert IPv4/IPv6 byte arrays to String representation.

* RFC5952-compliant IPv6 address shortening routine
[cooja] Get rid of all those redundant IP address to String functions

Commonly use the String representation functions of IPUtils.
[cooja] interfaces/IPAddress: Reimplementation of the IPAddress interface

New features:
* extended interface
* Shows all IPv6 addresses of a mote
* Shows link local IP in visualizer
* Reads IPs correctly from different memory layouts
Merge pull request #569 from ejoerns/pull-req/cooja-newip

[Cooja] Reimplementation of the IPAddress interface