Add TBar, TBarSeries, TSeries, TValue, and IFeed implementations with comprehensive documentation and examples

- Introduced TBar struct for efficient OHLCV data representation.
- Implemented TBarSeries class for high-performance collection of TBar instances using Structure of Arrays (SoA) layout.
- Added TSeries class for time-series data management with zero-copy access.
- Created TValue struct for time-value pairs with implicit conversions.
- Defined IFeed interface for consistent data feed implementations.
- Developed CsvFeed class for loading historical OHLCV data from CSV files.
- Implemented GBM class for generating synthetic financial data using Geometric Brownian Motion.
- Added Quantower project files for Averages indicator with necessary dependencies and configurations.
- Included extensive usage examples and notebooks for TBar, TBarSeries, TSeries, TValue, and feed implementations.

lib/core/tvalue/TValue.md

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+# TValue: Time-Value Pair
+
+## Overview
+
+`TValue` is the fundamental building block of QuanTAlib. It represents a single data point in a time series, consisting of a timestamp and a double-precision floating-point value.
+
+It is implemented as a lightweight `readonly struct` to ensure immutability and high performance (stack allocation, no GC overhead).
+
+## Structure
+
+```csharp
+public readonly struct TValue
+{
+    public readonly long Time;   // Ticks (UTC)
+    public readonly double Value; // Data value
+    public readonly bool IsNew;   // Metadata for streaming (optional usage)
+}
+```
+
+## Key Features
+
+*   **Lightweight**: 24 bytes (long + double + bool + padding).
+*   **Immutable**: Thread-safe by design.
+*   **Implicit Conversions**: Can be implicitly converted to `double` (returns Value) and `DateTime` (returns Time).
+*   **Performance**: Designed for high-frequency trading and large dataset processing.
+
+## Usage
+
+`TValue` is used throughout the library for:
+*   Input to indicators (`Update(TValue)`).
+*   Output from indicators (`Value` property).
+*   Elements in `TSeries`.
+
+## Constructors
+
+*   `new TValue(long time, double value, bool isNew = true)`
+*   `new TValue(DateTime time, double value, bool isNew = true)`