Improve ContributionType checking

### Problem Description

Disclaimer: This issue may be based superseded or incomplete knowledge.

AFIK the computation of the `ContributionType.GEOMTRY_CHANGE` is computation intensive. That's why, if you are not interested in that type, you should use the `OSMContribution.is(ContributionType contributionType)` method instead of `getContributionTypes()`.

Yet, this method cannot check for empty `ContributionType` and as https://github.com/GIScience/oshdb/issues/113 was unfortunately closed, I will still have to check for `GEOMTRY_CHANGE` to filter empty contribs.

### Expected Solution

Add a method to check for empty `ContributionType`.