Remove ConvertWithFunction and update classes using it

As each Function is a Converter now, we don't need a special wrapping
mechanism for that anymore. We simply can use any function
to act as a converter.
Introduce MinMax Interface and fix naming of MinMaxRealType
DefaultOpMatchingService: fix bug in Type resolution

The CommandModuleItem knows how to report its most specific available
generic type, as viewed from its own class, whereas calling
getField().getGenericType() is dumb and will only say "I am type T!"
without knowing the context of its T when viewed from a subclass.
Merge pull request #45 from imagej/minmax

Introduce MinMax Interface and fix naming of MinMaxRealType
ProjectorTest: Fixed way of getting Sum op.
NormalizeRealType: Remove used parameter
Fixed call of "normalize" in NormalizeII
MeanRealType: Fixed calls of ops
LocalMean: Fixed call of ops
LocalThresholdTest: Fixed call of op
Replace Create interface with CreateImg interface

* The current create interface, implies that the OpService can on basis
of the given parameters figure out what shall be created. Often this
is not the case. Imagine you simply pass a 'long[]'. The OpService can't
determine which type of Img it has to create. Actually its even unclear
that the output will be an Img.

* We have to introduce additional CreateXY interfaces, where XY is a
placeholder for certain types. CreateImg for example is inherited by ops
which create an Img given some output type and an ImgFactory.
Add various ops implementing CreateImg
Update DefaultOpService and OpService to work with CreateImg interface
README.md: Update example to use CreateImg
OpService: fix javadoc of createImg
OpService: deprecate OpService#create

That way, old code at least keeps working.
Merge pull request #46 from imagej/createimg

Refactor 'Create' interface to 'CreateImg'
POM: add Brian Northan to developers list

You rock, Brian!
POM: add missing developers and contributors
POM: tweak whitespace

This makes it consistent with the output of "mvn tidy:pom".