Fix of Arithmetic overflow on Perf Counters (#370)

If the perf counters for a server get too large, the query begins to throw an issue with an arithmetic overflow. Most specifically it throws an error:

> Unable to fetch from SQL: Arithmetic overflow error converting expression to data type money.

Instead of converting to money, this converts the value to a decimal(25,2) which at least covers my use case.

Author: NickCraver

Opserver.Core/Data/SQL/SQLInstance.PerfCounters.cs

@@ -69,14 +69,14 @@ And spi.object_name Not Like 'SQL Server 2016 XTP%'
        cc.counter_name CounterName,
        cc.instance_name InstanceName,
        cc.cntr_value CurrentValue,
-       (Case cc.cntr_type 
+       CAST((Case cc.cntr_type 
         When 65792 Then cc.cntr_value -- Count
-        When 537003264 Then IsNull(Cast(cc.cntr_value as Money) / NullIf(cbc.cntr_value, 0), 0) -- Ratio
+        When 537003264 Then IsNull(cc.cntr_value * 1.0 / NullIf(cbc.cntr_value, 0), 0) -- Ratio
         When 272696576 Then cc.cntr_value - pc.cntr_value -- Per Second
-        When 1073874176 Then IsNull(Cast(cc.cntr_value - pc.cntr_value as Money) / NullIf(cbc.cntr_value - pbc.cntr_value, 0), 0) -- Avg
+        When 1073874176 Then IsNull((cc.cntr_value - pc.cntr_value) * 1.0 / NullIf(cbc.cntr_value - pbc.cntr_value, 0), 0) -- Avg
         When 1073939712 Then cc.cntr_value - pc.cntr_value -- Base
         Else cc.cntr_value
-        End) CalculatedValue,
+        End) as decimal(25,2)) CalculatedValue,
        cc.cntr_type Type
   From @CCounters cc
        Left Join @CCounters cbc