Added new commands: addrolemember and removerolemember

[nagai-takayuki]

I added two new commands: addrolemember and removerolemember.

• addrolemember {role} to {idnumber1} {idnumber2} ... {idnumberN}
  add members with the specified role to groups with the specified idnumbers. Group idnumbers are assigned in group config.
• removerolemember {role} from {idnumber1} {idnumber2} ... {idnumberN}
  remove members with the specified role from groups with the specified idnumbers. Group idnumbers are assigned in group config.

In my use case, I use Moodle course as a kind of peer review system. With these commands, users with special roles (ex. editors, reviewers) are temporary assigned to specific groups according to editorial workflow.

[timhunt]

Thank you very much for working on this. This looks like a useful addition.

I am just wondering if we can improve the wording of the command to make it more obvious what it does? (It is very difficult to think of something which is clear.) What about?

groupsadd <role> to <idnumber1>, ...
groupsremove <role> from <idnumber1>, ...

Two other comments:

• It would be good to have unit tests to very the new code. (There are unit tests for the other commands.)
• I think the file classes/.command_removerolemember.php.swp should not be included in the comment.

Thanks again.