Code style cleanup (remove tabs, use wildcard imports? etc.)

[jan-niestadt]

There are still files with mixed tabs and spaces around. This tends to cause commit noise, inconsistent indenting in diffs, etc.

We should consider switching the import style to using wildcards. This will also reduce future commit noise. If we do this, we should clearly communicate it to anyone working on BlackLab, so everyone uses the same settings.

There are probably other small code style issues. We should do one big cleanup soon to get rid of these.

We should ensure we don't have any active feature branches with large changesets when we do this, or it might cause headaches when merging.

[jan-niestadt]

We should remember to update the included .editorconfig and IntelliJ and Eclipse formatter settings files if needed.