Querying user's name and groups membership

Two new sub-commands are introduced for the module-info modulefile command: username and usergroups. They respectively fetch the name of the user currently running modulecmd.tcl or the name of all the groups this user is member of.

These two new modulefile commands can help to adapt code to specific users or groups. Like for instance to instantiate a modulefile for each group the user is member of:

$ cat /path/to/modulefiles/foo/.modulerc
#%Module
foreach grp [module-info usergroups] {
module-virtual foo/$grp .common
}
$ id -G -n
grp1 grp2 grp3
$ module avail
--------------- /path/to/modulefiles ---------------
foo/grp1 foo/grp2 foo/grp3

username and usergroups sub-commands of module-info modulefile command are only supported on Unix platform.