Parameterize log levels and log formats

The log levels and log formats are now customizable through
dcache.conf.

New configuration properties:

dcache.log.level.file
dcache.log.level.pinboard
dcache.log.level.remote
dcache.log.level.events
dcache.log.format.file
dcache.log.format.pinboard

Target: master
Require-notes: yes
Require-book: yes
Acked-by: Albert Rossi <arossi@fnal.gov>
Patch: http://rb.dcache.org/r/5530/