HOME-Directory Bug, String Readability, Date Validation, Unused Variables, PEP-8

[michaelkrisper]

Made following changes to the code:

• Fixed issue with home directory on Windows (Windows has no HOME environment variable). Used os.path.expandvar("~") instead.
• Transformed the usage-string into a more readable form in the source (put it in a triple-quote-string to be able to remove all the explicit newlines and doublequote-escapes).
• Formatted strings for better readability
  • Using single quotes in string which print double quote, so that they doesn't need to be escaped anymore.
  • Use auto string concat over multiple lines in paranthesis (removed the + \ where possible e.g. in logging.warning(...)-calls)
  • Used format string instead of concatening the strings manually.
• Added check for a VALID date in the filename (e.g. 2013-37-81 is not a valid date). Also the date doesn't need to be in front of the string - it can be anywhere in the filename now (some digicams put a prefix to their images e.g. img1234...).
• Removed unused variables
• Enforced PEP-8 coding standard (just formatting).

[novoid]

Thanks for improving m2a! :-)