Backend/scheduler administration page improvements

A small list of improvements for the backend/scheduler page:

1. The worker listing takes too much space and does not allow for the visualisation of important information. It would be better to transform it into a table, in which each line corresponds to a host and each column shows the following information: IP address, cores (in-use/available), memory (in-use/available), beat.scheduler version. The color of the line can be color coded: light green means 100% free, light read means 100% occupied, light yellow means partially occupied.
2. The total number of cores affected to a queue should be displayed
3. The queue listing should also become a table with more compact information displayed.