Make log output disabled by default

Related to rhbz#1023081

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Add support for journald and syslog

Two new command line arguments:
    syslog=(on|yes)
        - disabled by default
        - logs a stack trace to syslog with LOG_ERR level

    journald=(off|no)
        - disabled by default
        - logs a stack trace to journald with LOG_ERR level
        - the stack trace is saved in STACK_TRACE field

Related to rhbz#1023081

Signed-off-by: Jakub Filak <jfilak@redhat.com>