Type constructor names should be case insensitive

[ndmitchell]

From https://code.google.com/p/ndmitchell/issues/detail?id=415

Searching for DateTime -> Double should be the same as searching for Datetime -> Double, i.e. type constructor names should be insensitive.

As a side effect, searching for DOUBLE should just search for Double, not suggest that you might have meant Double (as it does now).

Additional examples abound, so this would be quite nice to fix.