add isolated increment methods

[Dave Skender]

Implement incrementing scenarios to calculate the next indicator bar:

Internals

• base increment¹
• observer OnNext() handler

¹ uses cached data instead of inputs

Public APIs²

• base increment (system agnostic I/O), all needed inputs, appropriate TResult out
• external cached (like observer handler, but using external data storage interface), consider cache-aside design pattern.

² repoints internal cache, then uses internal base increment? this wouldn't perform well if provided data is re-written to memory, but am not sure how to handle CLR compliance otherwise with by reference.

Other considerations

• static time-series implementation (see below)

[Dave Skender]

For the static non-observable time-series implementation, an approach to explore might be in the following form; though, it may need be IReadOnlyList or IEnumerable base.

public static class Ema : List<EmaResult>
{
    /* saved properties + minimal quote cache */

    /* new quotes */
    void Add(TQuote quote) { ... }

    /* throw simple exception when quotes arrive out of order */
}