Add option for automatic code formatting

Currently, not all code is systematically formatted, which complicates
the contribution process, diffing, etc.

Add automatic code formatting based on Eclipse formatter rules and
impsort for "Organize imports"-style reformatting.

Provide formatting rules that are very similar to the current code
style.

Add a script ("script/reformat-code.sh") to simplify reformatting code
upon demand (it is not performed by default).

Signed-off-by: Christian Kohlschütter <[email protected]>

Author: kohlschuetter