Visualize virtual profit of indicator based trade signals

[rosasurfer]

For the requirements see #57

Implemented using the ZigZag indicator as an example:

• The indicator has a new input parameter TrackVirtualProfit. If enabled it analyzes virtual PnL of ZigZag reversal signals for the configured MaxBarsBack periods.
• Then the indicator creates a custom symbol stored in a second MT4 terminal, and writes the generated PnL timeseries to the price history of that custom symbol, using the history API. All timeframes are auto-generated from the source (here M1).
• The indicator updates the custom symbol in the second terminal in realtime.

Example ZigZag(50) on M1:

Inputs for above example with 200'000 bars back:

Created custom symbol:

Generated chart. That's a regular chart, not a single offline chart:

[rosasurfer]

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[chatgpt-codex-connector]

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[rosasurfer]

Current issue: As the History API is implemented in MQL the performance is rather bad.
Solution: Move the History API to the MT4Expander DLL which would make it more than 10 times faster.

For the moment it's important to have this working implementation. Improvements will come later.