trxcon/logging: print category, level and extended timestamp
Since we're heavily using trxcon in ttcn3-bts-test, the logging
output should contain as much information as possible. Ideally
we should introduce the VTY interface (see OS#3666) and get
logging configuration options as a bonus. But let's just use
some beneficial hard-coded defaults for now:
- print category and level (huh, we use NOTICE everywhere?),
- do not print category-hex (who needs it anyway?),
- print extended timestamp, so we're in synce with other logs.
P.S. This configuration is based on my own debugging experience.
Change-Id: Ie3d259f3255d8af80e6780f850b808fa243f97b4