Fix last data point check, and use Fraction::toDecimal() along with new condition check function for comparison.

Change the notification logic to only look at the last recorded value, instead of all values in the past hour.

Prevent future security concerns by explicitely emptying the $condtion variable if it doesn't match an available value.

Enter the data point in the database after notification conditions are checked, so that we don't have to account for it in that logic.

Use a subselect JOIN in query for displaying latest values, to ensure that only one of each value is returned.