[MRELEASE-1001] Support project version aliases

**[Romain Manni-Bucau](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=romain.manni-bucau)** opened **[MRELEASE-1001](https://issues.apache.org/jira/browse/MRELEASE-1001?redirect=false)** and commented

${project.version} should be supported and lead to the same processing as ${project.version} when the version set is ${foo.version}.

Note: it is really the aliasing which must be supported and not the value which can be "wrong" (2 libs can have the same version indeed)

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**Issue Links:**
- [MRELEASE-943](https://issues.apache.org/jira/browse/MRELEASE-943) be more tolerant with project version
(_**"blocks"**_)

Start by reading MRELEASE-1001 and the linked MRELEASE-943 to understand the existing version-handling context. Trace how the version set is processed and verify the requested behavior: an alias such as foo.version should receive the same processing as project.version, without relying on matching version values; add or update the relevant tests.

Written by the indexing model from the issue text.