Generate only required fields.

Special fields (like labels, servers and nodes) were generated for all
cases even if they where not requested to be displayed.
This slightly improves performances for very big filesystems.
Remove unused code since v0.911

Shine.Configuration.Configuration.get_client_nodes() was unused since a
long time. Remove associated unit tests too.
Ticket #170: Select module loading list depending on action and component

A list of LoadModules actions is built during creation of the action graph
by requesting each Action instance which modules it needs.