#438 Update documentation on team projects

[Jean-Christophe Helary]

https://github.com/omegat-org/omegat/pull/725

Document "Have "Commit Target Files" also commit statistics file:
https://sourceforge.net/p/omegat/documentation/412/

Specifically:

Add information about commiting statisitics files when target files are comitted.

Add information on managing a team project in the How to set up a team project chapter.

Standardize inconsistent uses of "project administrator" and "project manager" to just "project manager".

Let me know if there are any project management/maintenance tasks missing from the new section on managing a team project.

[Jean-Christophe Helary]

There is a new PR that can be merged.
https://github.com/omegat-org/omegat/pull/1552