Bug 4014

Now the user groups are no longer loaded in one shot in order to avoid a long wait time with a lot of groups (1000 groups for example).

A cache was put in place to load at the demand the groups by pages (yet a page of 60 groups). The cache does only maintain the subgroups of the current highlighted group (or all root groups if no group is highlighted). It is used both by the filtering panel (at leftmost side) and by the groups selection panel.

With the introduction of this cache, the groups pagination as well the 'all-groups' selection link in the groups selection panel have been updated.