YADE should support the JSch logging interface

Current situation

• YADE implements a Virtual File System that supports a number of data providers, e.g. SFTP protocol implementation by JSch library.
• JSch has no standard logging facade like log4j or slf4j, but a custom com.jcraft.jsch.Logger interface
• YADE not supports the JSch logging interface

Desired behavior

• YADE should bridge JSch internal log calls to slf4j