Display quota consumption in the webui.

Currently, the Roles table in the webui displays allocation and quota guarantees / limits. However, quota "consumption" is different from allocation, in that reserved resources are always considered consumed against the quota.

This discrepancy has led to confusion from users. One exampled occurred when an agent was added with a large reservation exceeding the memory quota guarantee. The user sees memory chopping in offers, and since the scheduler didn't want to use the reservation, it can't launch its tasks.

If consumption is shown in the UI, we should include a tool tip that indicates how consumed is calculated so that users know how to interpret it.