Return root node even though everything is filtered.

[sdedic]

Two fixes:

• first, the Scope was designed to be equals based on its name only; the implementation Class was checked by mistake.
• maven implementation happily filters out even the root of the project when scope filter is active. This is bad, because all data under the root are lost. This PR handles the root conversion specially - root corresponds to the project itself and needs to be present always, so the filter is disabled for it.

[lahodaj]

I am sorry, but this is wrong. I accept that two scopes with different implementation classes but the same name should be equal, but then please do something like:

if (!(obj instanceof Scope)) {
    return false;
}

I believe generally equals is expected to not crash on CCEs, even if an object of an unrelated type is passed in.

[sdedic]

Uh oh ... mea culpa. Of course.

[sdedic]

Merged fix into the main commit before merge.

[jhorvath]

Looks good