Make the log level for command lines configurable

  In certain use cases, it is desirable to be able to change the log level
  at which cpptasks-parallel logs the command lines called for external
  commands, e.g. when the command lines are meant to be parsed by, say,
  Eclipse's CDT to make nicer logs.
Merge pull request #5 from TotallyPro/master

Top level config option to log command-line for eclipse to parse... default off