feat(Delta): add average delta line (SMA/EMA) over the delta histogram

[AlbertoAmadorBelchistim]

Summary

Adds an optional moving average overlay on the Delta histogram, hidden by default.

• Average mode: SMA or EMA over the per-bar delta value.
• Color mode: Fixed (base color), Zero cross (sign-based), or Slope (direction-based) per-bar line coloring.
• New Average group on the Visualization tab: ShowAverage, AveragePeriod, AvgMode, AvgColorMode, AverageColor, AvgSlopeUpColor, AvgSlopeDownColor, AverageWidth. All properties are tagged with [Tab] following the settings categorization.

Implementation notes

• O(1) rolling SMA (queue + running sum) and standard EMA; state resets at bar 0, no look-ahead.
• The average series is appended at the end of DataSeries and stays hidden unless enabled, so existing templates and workspaces are unaffected.
• The diff is additive-only (237 added lines, no reformatting) on top of current Develop.

Localization

Property names, group and tab reuse existing resources: Strings.ShowAverage, Strings.Average, Strings.AveragePeriod, Strings.CalculationMode, Strings.SMA, Strings.EMA, Strings.Width.

The color-mode strings have no matching keys in OFT.Localization yet, so they are declared inline following the same transitional pattern as the Half Gap settings in DailyLines, ready to be swapped once keys exist:

Text	Where
Color mode	AvgColorMode display name
Base color	AverageColor display name
Slope up color / Slope down color	slope color display names
Fixed / Zero cross / Slope	AverageColorMode enum members

Testing

Built against Alpha configuration with 0 errors. Smoke-tested on chart: toggle on/off, SMA↔EMA switch, all three color modes, period bounds (1 and 1000).

[Stig4all]

The moving-average calculation needs correction before merge.
OnCalculate can run repeatedly for the same forming bar. The SMA currently enqueues each call as another sample, while the EMA advances its accumulated state on every call. Both results therefore depend on how many updates a bar receives, rather than only on the per-bar delta values.
For example, with SMA(3), bars containing 10, 20, 30, and the last bar subsequently changing to 60, the implementation produces approximately 36.67 instead of 30.
Please make both calculations handle repeated updates to the same bar and verify that live results match a full historical recalculation. The remaining inline UI strings also need localization.

[AlbertoAmadorBelchistim]

Thanks, fixed:

• Both averages now depend only on per-bar values. The input is stored by bar index, the SMA keeps a running sum per bar (sum[bar] = sum[bar-1] + x[bar] - x[bar-N]), and the EMA starts from the stored value of the previous bar. Repeated OnCalculate calls for the forming bar overwrite the sample instead of adding one. Your example (SMA(3), 10, 20, 30 → 60) now gives 30.
• Verified with a harness that runs the actual CalculateAverage with 1–30 random updates per bar over 1,500 bars and compares it with a single-pass historical calculation and a textbook SMA/EMA, for periods 1, 3, 20 and 200. Live and historical values (and colors) are identical.
• Localization: the inline strings are gone. The coloring options now follow the built-in SMA/EMA indicators (ColoredDirection, BullishColor, BearishColor, all existing keys); the line color and width are configured on the series itself.