An empty resource hould not always be displayed as a zero resource. A
resources passed in as '' can mean different things. Handle an empty
value for a resource based on its context in the web ui: 0 for usage and
n/a for limits.

Fixes: apache#32

The web UI could not handle the queue absoulte resource usage if it was
not a integer value. The usage could also be n/a if not tracked. The web
UI now handles this correctly for all resource types.

Fixes: apache#33

Add a new node page displaying the scheduling nodes.
Side change: removal of the last job references.

Fixes: apache#34

Include new make target for a license check, consistent with the other repos: check-license.

…or-yunikorn-web into YUNIKORN-146

…build

…-web into YUNIKORN-146

This reverts commit b07de8c.

…image