Add support for idle_vms_total limits in the frontend
Merge remote-tracking branch 'origin/v3/5519' into v3/5519_v2

Conflict resolved by applying the patch bits by hand:
	frontend/glideinFrontendElement.py
Add documentation for group.config.idle_vms_total (introducted in this branch),
as well as group.config.running_glideins_total (for which the code was added long ago).

The explanation of the whole group.config section was rewritten to make it more clear.
Correcting minor doc problems
Add a little better text in the documentation
Add documentation for group.config.idle_vms_total (introducted in this branch),
as well as group.config.running_glideins_total (for which the code was added long ago).

The explanation of the whole group.config section was rewritten to make it more clear.
Correcting minor doc problems
Add a little better text in the documentation
Merge branch 'v3/5519' into v3/5519_v2
Merge branch 'v3/5519_v2' into branch_v3_2