Purpose: add some small features to the logger.

List of features:

• Changed file creation in the special way: user now have an ability to write logs in the custom file in the different modes;
• Added new severity: warning;
• Added conditional logging macros;
• Added ability to change time zone;
• Added ability to turn on/off the colours in the console appender;
• Added custom colours choosing (for the text and text background separately) for the console appender;
• Added ability to turn console appender's colours on/off.

Bugs, which are fixed:

• README was edited: now in part "Inspired by" correct link to the PLOG project.