Description of problem:
The Availability on the Monitor - "Graph" view is incorrectly calculated.

Version-Release number of selected component (if applicable):
JON 2.3.0GA, JON 2.2.0GA

How reproducible:
Tested on various JON servers and all of them showed the same behavior.

Steps to Reproduce:
1. On any monitorable resource, select the "Monitor" tab
2. Click the "Availability" view
3. Notice the "Availability" value.
3.1 At the bottom of the screen, roll to the last page (in the index 1, 2, 3 etc) and write down the first date of collected metric
4. Click the "Graphs" View
5. On the timespan selector on the bottom of the screen, select "Advanced Settings"
6. Select "Within a date range" and in the From: field select the date you recorded on the step 3.1
7. On the To: field, select the actual date & time
8. Plot the graph and read the "Availability" value
  
Actual results:
The values doesn't match

Expected results:
Matched values

Additional info:
Looks like the metrics are calculated using the red/green buckets/dots in the "Graphs" view instead of doing some more elaborated calc that's performed on "Availability" View.