to reduce the number of levels of nested if, for, or while statements

after paid from individual settlement fund, cancel the rest

Rename "bad-debt settlement method" to "black swan response method"

by calculating with new current_feed after filled a call order

by calculating with new current_feed after filled a call order

when feed price is updated and the new limit order is fully filled

check limit orders first when feed price is updated

when current_feed got updated, some existing limit orders may be filled

check limit orders again after matched a call order with a settle order

and slightly refactor other code

to other types when exists an undercollateralized debt position

by moving some assertions from do_apply() to do_evaluator()

* check call orders after updated/closed a debt position
* always allow increasing CR if not to increasing debt
* allow partial fill if triggers margin call and new CR > ICR

to reduce the number of levels of nested if, for, or while statements

check capping and uncapping of current feed price

by using database::find_least_collateralized_short()

after filled a call order with a settle order

Settle undercollateralized debt position when unable to match with a limit order

and fix individual settlements: always check limit orders again
after individually settled some debt positions