Change pre-increments to post-increments for the whole repository

[stefanhahmann]

In java usually post-increment is used (e.g. i++) and pre-increment (e.g. ++i) only in cases, where it is needed by the program logic.

In this repository there are some places, where pre-increment is used, even in cases, where it is not required by the program logic. These cases should be changed, as it makes the source code more compliant to usual practices in Java.

Originally posted by @maarzt in #4 (comment)