Filter out duplicated dependencies from pom.xml

[yevhenii-nadtochii]

This PR addresses #362.

As described in the issue, sometimes we can't overcome the presence of several versions of the same dependency. pom.xml is generated upon a whole project and doesn't group dependencies by modules. Specific modules override versions dictated by config. And, as a result, several versions of the same dependency leak to pom.xml.

spine-time repository is an example here. Each subproject is configured to use a specific version of protoc from config. The configuration is performed from the root project:

 protoc {
    artifact = Protobuf.compiler
}

Meanwhile, time module applies our mc-java plugin, and not the last version. The plugin overrides the version of protoc, specified by the root. As a result, the module uses its own version.

---

This PR makes DependencyWriter filter out duplicates by group and name. Only the one, with the newest version, is retained. The duplicates are logged.

Generation of license reports is not changed, since dependencies there are grouped by modules.

[yevhenii-nadtochii]

@armiol @alexander-yevsyukov Please, take a look.

[armiol]

Please log some details on the duplicates, as we discussed.

[yevhenii-nadtochii]

@armiol PTAL

[armiol]

LGTM.