Indicator: Implement method utilizing BandsOnArray on the idata

[kenorb]

• Class: Indicator/Indi_Bands
• Branch: dev-indicator

The method should accept mode for which to calculate the value (by default 0, some indicators could have multiple modes/indexes), and results can be stored in another variable, e.g. ibands/ibands[mode] (of Buffer or BufferStruct type). The storing values can be either doubles or even better is to use struct, e.g. BufferStruct<IndicatorDataEntry> ibands (to support storing of 3 values per indicator data entry: BAND_LOWER/BAND_BASE/BAND_UPPER).

Input values can be similar to #156 (start_bar ot start_pos and count).

Refs:

• MQL4: https://docs.mql4.com/indicators/ibandsonarray
• MQL5: https://www.mql5.com/en/forum/245375 (custom implementation)
• Logic example: Indicators/Examples/BB.mq5 (see: StdDev_Func()).

[kenorb]

Can we add iBandsOnArray method to Indi_Bands class, similar as in #166 and #175?