Set up event handler for compute metric buttons

Just added a bit code to the controller, view and JavaScript code to
assign functionality to each button responsible for issuing a worker.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add compute all button and status table column

It should be possible to compute all metrics on a certain repository, as
well as all metrics on all repositories. To introduce this I have added
a button. The additional status table column should be used to display,
whether there are metric results available and/or from when.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Generalize worker instantiation process

I have generalized the worker instantiation by using the repository and
metric parameter values. Based on the values two arrays are generated.
One for the repositories on which the metrics should be computed and one
determining which metric should be computed.

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