Leaving "softly" an hidden group

[imath]

1/ When you leave an hidden group from the link of the group header or from the siteurl/members/username/groups list of groups leads you to a 404 and the confirmation message is not showed.

2/ When you leave the hidden group from the groups directory 'my groups' scope, once the ajax request is done it leaves the container li, so if you click on the group link, then you have a 404.

I suggest the diff attached to this ticket to :
1/ redirect to siteurl/members/username/groups if the group status is hidden
2/ slide up the container li if the group status is hidden.

[boonebgorges]

Good find, imath. Let's do this in 1.9.

[r-a-y]

In 7384:

Fix redirect when a user leaves a hidden group from the group's page.

Usually when a user leaves a group from the group's page, it redirects
back to the group's homepage, however for hidden groups this creates
a 404.

This commit redirects the user back to their list of groups when
leaving a hidden group.

Commit also adds phpDoc and uses some API functions instead of the $bp
global.

Fixes #5077. Props imath.

[r-a-y]

In 7385:

Tweak JS when joining or leaving a group from the groups directory.

This commit does the following:

• When leaving a hidden group, it removes the hidden group from the group loop.
• Increases or decreases the "My Groups" count if you join or leave a group.

Props imath for the initial patch.

See #5077.