Rename AddConstantToImage and remove comments

This class adds a constant to an image in place, so let's call it
AddConstantToImageInPlace for now.
OpService: add method to get the best op instance

This is similar to the lookup method, except that it unwraps the
resultant Module back to an Op. This is useful in cases where that Op
will be used as input into another Op.
AddConstantToImageFunctional: remove comments
UnaryFunction: fix author ;-)
Move common input/output logic up to UnaryFunction
Rename DoOpOnImage

It applies a UnaryFunction across an antire image in place,
so let's name it that way: ApplyFunctionToImageInPlace.
Make AddNumericTypes extend UnaryFunction & rename

The new name is AddConstantToNumericType, since it
is more consistent with the AddConstant*Image* ops.
DefaultOpService: fix bug in lookup routine
ApplyFunctionToImageInPlace: simplify

No need to wrap in a module -- we can directly call compute(in, out).
Merge branch 'lifting'

Conflicts:
	src/main/java/imagej/ops/DefaultOpService.java
	src/main/java/imagej/ops/threshold/PixThreshold.java
Gauss: fix javac compile error