Some cleanups and improvements of source code documentation.

Signed-off-by: Tobias Lorenz <tobias.lorenz@etas.com>
Some cleanups and improvements of source code documentation.

I would like to understand what RefTimeKeeper does...

Signed-off-by: Tobias Lorenz <tobias.lorenz@etas.com>
Fix some warnings of categories C4018, C4100, C4129, C4244, C4553, C4996.

What else...
* Replaced MS-specific _stprintf with standard sprintf.
* FilterName migrated from char[] to std::string.

Signed-off-by: Tobias Lorenz <tobias.lorenz@etas.com>