Filter unit scopes while typing unit name

[delphidabbler]

Currently (v0.2.0-beta) we have to enter a unit name in the Name of unit edit box then click the Find Namespaces(s) button before being presented with a list of possible unit scopes.

It would be much friendlier to start to display the list as the user types in the Name of unit edit control, so that the list gets filtered as the user types.

[delphidabbler]

Should the list be filtered every time the user presses a key in the Name of unit edit box, or should there be a limit on how many times the lookup is performed, say doing nothing unless a certain time had elapsed?

Will the filtering need to be done in a background task?

Should the filtering not start until, say, 3 letters have been typed?