Provide an index or counter for each/find/findAll/collect and friends by taking into accounts the arity of closures passed to them

As per the suggestion on this thread:
http://www.nabble.com/generic-%27withIndex%27-method-%28like-Ruby-1.9-with_index%29-ts25631548.html

The idea is to have access to an index or counter in all the functional methods iterating over collections, by using an additional parameter in the closure passed in parameter of those methods. That way, we don't need to add as many *withIndex variant methods to the existing ones, but rather provide a convenient convention.

Some examples with each, and similarly by replacing each with find/findAll/any/every/collect and perhaps inject:

list.each { elem -> ... }
list.each { elem, counter -> ... }

map.each { entry -> ... }
map.each { key, value -> ... }
map.each { key, value, counter -> ... }