Skip analysis of non-solution files

[sanderploegsma]

Some exercises consist of more than one file in the src/main/java folder, and some of them are designed to be read-only files. These are marked as such in the exercise's .meta/config.json file, because they should be listed in the files.editor list.

For example, the configuration for the wizards-and-warriors-2 exercise lists the following files as read-only:

• src/main/java/Character.java
• src/main/java/Destination.java
• src/main/java/TravelMethod.java

The goal of this issue is to make sure that read-only files are never processed by the analyzer.

In most cases processing these files may not introduce any issues, but just in case one of them contains code that triggers an analyzer comment we should skip them by default. If not, a student may receive feedback on a file that they did not write and cannot edit, which is just confusing.