Fix progress bar bug for the worker progress

I am not 100% sure, but I think adding an additional worker.at statement
to the compute method resolved this bug of filling the progress bar up
more then once for the compute state. This commit fixes #31.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Replace boolean metric status with icons

For displaying whether a certain repository has already a metric score
assigned I simply printed true or false. Now I have moved the helper
method and display either a check mark or a cross.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add spinning wheel to display work in progress

For the administration control panel I have added another visualization.
A spinner is used to display work in progress. For instance, while the
metadata records are loaded, results written back, etc. In these cases
the progress bar does not move, but work in progress is communicated.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Implement progress bar to display overall progress

Addressing issue #30 I have implemented another progress bar to display
the aggregated progress of all jobs. This commit fixes #30.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>