Remove unused or obsolete methods from Iterables2

[HannesWell]

This change is based on the assumption that the class Iterables2 is considered an internal helper and not a user facing API.

If that assumption is wrong, this change would indeed breaking change for users.

[NiklasRentzCAU]

This looks like a good simplification, especially using the reduce function instead of implementing it with this fold function. However, I cannot really test this change, because I have never used these exportBrandings or even really know how they were used. Do you have some test for this change that you could provide as well?

[HannesWell]

This looks like a good simplification, especially using the reduce function instead of implementing it with this fold function. However, I cannot really test this change, because I have never used these exportBrandings or even really know how they were used. Do you have some test for this change that you could provide as well?

I just modified our Eclipse product product a bit so that they are used and after fixing a few bugs (see #210 :) ), it worked perfectly fine.
So I can confirm it works as expected, but I cannot provide a standalone test case for it. I hope that's sufficient.