Add Price Volume Trend (PVT) Indicator and Tests

- Implemented the PvtIndicator class for calculating Price Volume Trend in Quantower.
- Created unit tests for the Pvt class to validate calculations and state management.
- Added validation tests to ensure consistency with OoplesFinance's implementation.
- Developed a comprehensive documentation (Pvt.md) explaining the PVT concept, calculations, and usage.
- Included methods for batch calculations and streaming updates for PVT.

lib/volume/nvi/Nvi.cs

@@ -124,7 +124,8 @@ public sealed class Nvi : ITValuePublisher
         }
 
         // Calculate NVI - only update when volume decreases
-        if (s.Index > 0 && s.PrevClose > 0 && s.PrevVolume > 0 && close > 0 && volume < s.PrevVolume)
+        // Matches PineScript: if not (na(src) or na(vol) or na(src[1]) or na(vol[1]) or src[1] == 0.0 or vol[1] <= 0.0) and vol < vol[1]
+        if (s.Index > 0 && s.PrevClose > 0 && s.PrevVolume > 0 && volume < s.PrevVolume)
         {
             s.NviValue *= close / s.PrevClose;
         }
@@ -268,7 +269,8 @@ public sealed class Nvi : ITValuePublisher
             }
 
             // Only update when volume decreases (using sanitized values)
-            if (prevClose > 0 && prevVolume > 0 && currentClose > 0 && currentVolume < prevVolume)
+            // Matches PineScript: if not (na(src) or na(vol) or na(src[1]) or na(vol[1]) or src[1] == 0.0 or vol[1] <= 0.0) and vol < vol[1]
+            if (prevClose > 0 && prevVolume > 0 && currentVolume < prevVolume)
             {
                 nvi *= currentClose / prevClose;
             }