Re-introduce proper logging

[clhunsen]

With the rewrite in Python, the ability of logging got lost. This need to be re-introduced.

Requirements

• logging for each project in input file independently

• insert a header with the configuration of cppstats

  =================================================================
  cppstats <version>
  project: <absolute path of project folder>
  [preparation: <kind of preparation>; <absolute path>]
  analysis: <kind of analysis>; <result file(s)>
  =================================================================
  
  [<preparation log>]
  
  =================================================================
  
  <analysis log>
  
  =================================================================
  End Time: <time>
  =================================================================
  

  The second row should depend on the CLI argument --filenamesRelative.

• adjustable log-directory

• log files should be named by <timestamp> <project's basename>.log.