Allow user configure new loggers through environment variables.
To configure it user must set the env LOGGER_CATEGORIES in the following pattern:

package:level,another.package:level

BLANK Level defaults to FINE

i.e: LOGGER_CATEGORIES=com.my.package:TRACE, com.my.other.package:TRACE
results in:
<logger category="com.my.package">
<level name="TRACE"/>
</logger>
<logger category="com.my.other.package">
<level name="TRACE"/>
</logger>