Add support for changing log directory

The current implementation writes to a file in CWD.

This patch allows users to pass a path to a directory in output command
line argument. If a value of the output argument points to a directory,
the log file path is set to $output/abrt_checker_$PID.log

Related to rhbz#1023081

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