imfile: replace obsolete legacy sample, add sample with wildcards

[rgerhards]

trafficstars

The current obsolete legacy sample should be converted to new style. Obsolete format shall be removed (else folks continue to use it).

[roshan8]

Yeah :) I was trying to use it with wildcards from past 2 days :/

[rgerhards]

We should also cover a sample for this: https://github.com/rsyslog/rsyslog-doc/issues/474