Unable to get authToken/tokenType from existing GitLabApi instance

[slonopotamus]

Subj. This is needed to

1. Clone instances of GitLabApi in order to perform safe sudo in multithreaded environments (see sudo functionality is inconvenient #118)
2. Save token for later use

[gmessner]

Getters for the token info have been added as well as a GitLabApi.duplicate() method, and available in release 4.7.9.