Version 0.6.0

Version 0.6.0

Changelog:

- NMEA:
  - AIS helper functions moved into its separate files.
  - changed type of talker id from 'std::string' to its own type.
  - consistency of macro names, exported by headers, all start now with 'MARNAV_'.
  - explicit specification of copy/move construction and assignment.
  - fix type of PGRMZ is now an enumeration.
  - most fields of RTE are not optional.
  - removed macro 'MARNAV_NMEA_GETTER'.
  - renaming enumeration 'positioning_system_mode_indicator' to 'mode_indicator'.
  - sentence BWR missed the mode indicator.
  - sentences HDT, PGRMM and PGRMZ added.
  - unit of nautical mile corrected to 'NM'.
  - added functions to get printable names for constants.

- AIS:
  - enumerations moved from message_21 to namespace 'ais'.
  - explicit specification of copymove construction and assignment.
  - getter for nagivation status added to message_01.
  - latitude/longitude of messages are now handled using utils::optional.
  - maneuver indicator is now an enumeration.
  - ROT not available now implemented as constant expression.
  - added functions to get printable names for constants.

- Examples:
  - bug fix: rendering contents of nmea::rte.

- Tools:
  - Tool 'nmeadump' added to print decoded NMEA sentences and AIS messages
    in human readable form.

- Doc:
  - build status (Travis-CI) removed from README.

- Build:
  - added script to build all relevant configurations for testing.
  - build script 'bld' added, build configs added, replacing prepare scripts.
  - conditional build for nmeadump, depending on library configuration.
  - support parallel builds in build scripts.

- Dev:
  - bug fix: ctags/cscope target not created if ctags not found.
  - consistent formatting with clang-format-3.9
  - ctags target separated into its own cmake module.
  - disable clang-3.9 on travis-ci, currently not supported.
  - enabled clang builds on travis-ci.
  - formatting is now consistent again.
  - get git information using functions, information is not extraced automatically anymore.
  - script added to perform benchmarks for multiple branches.
  - Travis-CI upgrade of CMake to 3.6.2
  - update of the local vim config.
  - upgrade from Clang-3.7 tools to Clang-3.9

- TODO:
  - added considering std::chrono to be used in nmea/time.