add possibility to log objects to log functions

[jogibear9988]

at the moment many people are logging data like this:

  adapter.log.debug('blabla ' + JSON.stringify(obj)) 

wich is inefficient, cause the JSONS to string conversation is also done, even if loglevel is not active! would be better if we could do this:

 adapter.log.debug('blabla ', obj)