#419 Extension or API to allow custom sorting of completions

[ddoubledaysf]

I am a developer working on extending PyDev for our custom development environment. Usually when I request code completion, the canddates that begin with underscore character are of the least interest, but they always sort to the top. I thought perhaps I could change this behavior in my extension, but in the code I see that the static final IPyCodeCompletion.PROPOSAL_COMPARATOR is always used for sorting the candidates. The feature request is to have the code use a pluggable Comparator provided by either API or extension point.