[tycho-version-plugin] only current project version is updated when project references another pom

[laeubi]

Assume we have a root project R and it has a module mentioning another pom project P that now includes modules M1 ... Mn executing the version update results in only project R updated while one would assume that R, P and M1 ... Mn are updated.

The problem is that only for the initial file a version update is created and then there must either be this file or the other must use it as a parent to be updated.