Update aggregator to new format

[florence]

Please update the README when this is done.

The aggregator should parse log files containing lines with the following format:

<HOST>:<EVT-TYPE>:<HOST-TYPE>:<TIME>:<TTY>

<HOST> := some string
<EVT-TYPE> := login
                      |  logout
<HOST-TYPE> := CCIS-WINDOWS
                        |   LINUX-LOCAL
                        |   LINUX-REMOTE 
<TIME> := unix timestamp
<TTY>   := ttyN
             |   ptsN

Where N is a number. All hosts of type CCIS-WINDOWS should have a 'tty0'

When put into the backend all records should be considered unique, so we need to make sure no duplicate data is uploaded

[florence]

Change to the format (again):
{host:,evt-type:,host-type:,time:,tty:} (ie JSON format)
The TTY field is optional. It will not be present for windows, and will be for linux. If it is not present interpret it as some 'undefined' value.