web: add logging configuration

Currently we have no logging implementation
connected in run time which makes log messages are lost.

This change adds logback as SLF4J implementation.
Java.util.logging is bridged to slf4j.

By default application logs to /var/log/mgmt.log.
The log directory can be changed by seting 'log.dir'
system property.

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>
Do not crash shell if /tests does not exist

Signed-off-by: Tomasz Grabiec <tgrabiec@cloudius-systems.com>