getProject and getGroup API are inconsistent about escaping

[novalis]

Just noticed this one:
https://github.com/timols/java-gitlab-api/blob/master/src/main/java/org/gitlab/api/GitlabAPI.java#L379
vs
https://github.com/timols/java-gitlab-api/blob/master/src/main/java/org/gitlab/api/GitlabAPI.java#L617

The source is b5a3ca4#diff-ba8070528e9e2174d6a7cefcf0871f93L367 from @djayard.

getProject needs the group to be not escaped, while getProject needs it to already be escaped. PR coming momentarily.