- add datalog plugin which can be used to write item status into
  different log files
- support multiple datalogs in item configuration
- remove prefix in logger messages - already added by the system itself
- change field separator from "|" to ";"
- update field separator
- add var/log/data directory for datalog plugin
- fix headline
Merge pull request #60 from ohinckel/dev-plugin-datalog

New Plugin DataLog: Provide easy logging mechanism for items