v2_rc1: Bump version to 2, finally.

• New netctl flow node added (as module), as well as agent API for
  that infrastructure
• Complete overhaul of LWM2M API & implementation, now with: access
  control objects support, authorization, UDP channel security (via
  DTLS)--with simmetric or asymmetric keys--, Raw Public Key, etc. The
  API was split into multiple files (mostry client/server separation),
  and many bugs in that code were fixed.
• MQTT module got a fix for when connecting to a broker failed
• IIO: fix for when devices were not activated before reads take
  place, support for IIO mount matrix, support for sampling frequency
  to channel level, support for hrtimer-based trigger, support for
  multi-channel reading on devices, new C-API to read configuration
  attributes including scale, offset and sampling frequency, support
  for wildcards on IIO paths and other minor issues.
• libmicrohttpd: the minimum required version was wrong, now fixed to
  0.9.47
• libmosquitto: the minimum required version was wrong, now fixed to
  "1004002"