Clean up log4j and slf4j configs

Removed log4j.xml and adapted its contents into log4j.properties
Created log4j-dspace-cli.properties for command-line output
Modified dspace CLI tool to use log4j-dspace-cli.properties

After merging this changeset, we will need to clean up JAR files on servers to prevent slf4j messages from ending up in the tomcat logs.

See http://wiki.datadryad.org/Logging_Technology for more information