Adds method to make order values match the fractional actuality

[MarkoPaasila]

I suggest this is merged only once a strategy or two makes use of it.

Partial solution to #511.

[MarkoPaasila]

Just to clarify how the method works.
It uses internal amounts (integers). The smaller internal amount - which isn't necessarily the smaller absolute amount - is determined first, because it has less resolution. The other amount is determined next, because it has more granularity and can be better adjusted according to the first amount - to result in a price that matches the target price as closely as possible.

Eventually we can expand the method so you can ask for price, quote, or base to be rounded down or up. For now, it just gets the closest possible fractional value and returns it as float

[thehapax]

A few things.

1. The name of the method is a bit confusing. perhaps " onchain price", as the word "fix" is non specific
2. Can you provide an actual use case here with a unit test.
3. returning 3 items or more, typically should be avoided, in general it would be better to return a datastructure like an arrayy, but clarification is needed in how would be used in a strategy. and if you actually need to return all 3 items.

[MarkoPaasila]

1. I'll change that
2. I'm yet to learn unit tests. But since this isn't urgent, we can let this linger until I have done it.
3. It returns a dict, or doesn't it? I think it's necessary to return all 3 values, as they are all changed in the function, and we don't know which one of them will be used,

[thehapax]

2. I'm yet to learn unit tests. But since this isn't urgent, we can let this linger until I have done it.

Actually unit tests are the main priority at the moment. It might be of benefit to see how it actually works. I'll send you references via chat.

[thehapax]

Hi @MarkoPaasila, as the base.py methods for price handling have been moved to BitsharesOrderEngine and this pull has conflicts, would you kindly resubmit a pull with fresh updates?