Add status label for failed metric computation

I have added a status label to display if an error has occurred. This is
not integrated very well. I am going to consider a state machine for the
interface. Otherwise I will run over and over again into a lot of bugs.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Refactor JavaScript for scheduler

I am refactoring the JavaScript code the scheduler, hoping to get to a
point where it is more robust and easier to maintain.

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

The status loop which continuously calls itself until all jobs are
finished works now again.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Make interface more responsive

By resetting the job status of a certain metric at start of the
calculation the progress bar gets filled up again. This improves
the responsiveness a bit makes the interface more lively.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add path and logic to return last updated field

I have added a last_updated route in order to provide the possibility to
dynamically update the last updated display without reloading the page.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Update the last updated display after completion

Now the last updated display in the scheduler view is also updated
dynamically after the job has finished.

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