New CLI command: dump

This will add a new CLI command named `dump` which display additional information for a given item. It could really be handy when trying to debug something (e.g. logics) to know the items current state and all information related to an item (e.g. previous value, last change, ...).

Example output:

```
> dump env.core.memory
Item env.core.memory {
  type = num
  value = 14188544
  age = 56.113745
  last_change = 2014-11-18 21:34:38.136741+01:00
  changed by = Logic:None
  previous value = 0
  previous age = 14.555422
  previous_change = 2014-11-18 21:34:23.581319+01:00
  config = {
    sqlite = init
  }
}
> 
```