allow requesting a set of resources from a specified pool

If the number of resources is a positive integer, the job will try to
reserve N resources among the specified ones.

The reserved resources names will be stored in a build variable whose
name is specifiable in the job configuration.

Signed-off-by: Aki Asikainen <aki.asikainen@kone.com>
Signed-off-by: Robin Jarry <robin.jarry@6wind.com>
allow manually reserve/unreserve resources in the lockable resources panel

All logged-in users are allowed to reserve free resources. A resource
can only be unreserved by the user that reserved it or by an
administrator.

Signed-off-by: Aki Asikainen <aki.asikainen@kone.com>
Signed-off-by: Robin Jarry <robin.jarry@6wind.com>