Define code style for j-Ecdar

[magoorden]

The code base for j-Ecdar is not checked for adherence to any style, because we haven't defined a style for our code. As a result of this, multiple styles are used throughout the code, which makes it less consistent.

In another Java-based tool, we are using Checkstyle to specify and automatically check the style of the code. There are style specifications, like Google's Java style, which we can use as a basis for our project.