Support BOM incremental changes part 2

[famod]

Follow up to #241. This is about the much more complicated part of trying to detect which dependency has changed inside a BOM to then only build the modules actually depending on this dependency (or dependencies).

[famod]

For later reference:

• https://stackoverflow.com/questions/39935160/how-to-use-jgit-to-get-list-of-changes-in-files/39935835#39935835
• https://stackoverflow.com/a/18378006/9529981