statistics: deprecated statistic extraction interface removed.
statistics: fulfill_dependencies() fixup.
bindings/python: Statistics class removed.
bindings/python: statistic extraction method added to Data class.
combaine: update to combaine (>= 0.6.5.6).
backends/file_logger: write to log file with append mode.
backends/file_logger: if during file_logger activation error occured method run() returns false and error message is accessible via m_error member.
backends/file_logger: if handystats processing core is not initialized file_logger activation will fail with appropriate error message.