These fields are only relevant in field templates (i.e. mongodb): a
field for a non-existent CEE property is not created (instead of being
set to an empty string).

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

Let msg.c handle appending fields, which also allows it to append more
than one field per replaced property.

The result allows supplementing CEE data with other (non-constant)
properties, but will currently result in duplicates if $!all-json and
the template contain fields with the same names.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

The mongodb test contains only debug printfs.

Example template, inspired by writeMongoDB_msg:

$template MongoTemplate,"%hostname::::sys%%timereported::::time%%timegenerated::::time_rcvd%%msg%%syslogfacility-text::::syslog_fac%%syslogseverity-text::::syslog_server%%syslogtag::::syslog_tag%%programname::::procid%%procid::::pid%%$!foo::::foo%%$!abc::::renamed%"

Note that JSON escaping is actually undesirable in this mode (should it
be silently ignored?), $!all-json doesn't yet work as expected, and all
data is stored as strings.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

This does not yet do anything.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

Conflicts:
	runtime/msg.c