Strange and unreliable feedback when target min == max

[helgoboss]

Strange because of strange normalization behavior if value == target min == target max (it returned min in that case, but it would make more sense to return 1.0).

Unreliable because of numerical inaccuracies when querying actual parameter FX values (they can deviate from the requested value, e.g. you request 0.2 and get 0.19999999423128). Usually that's not an issue but if target min == target max we have don't have a range of values anymore but just one particular value - and then it's an issue for getting the right feedback value.