Animate filling transition

For the circular progress bar I have modified the code in a way, that
the filling transition is now animated.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Encapsulate metric meter into a class

For purposes of reuse I have refactored the code for creating and
animating the metric meter into a separate class.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add click event to trigger metric computation

I have implemented a click event for the metric meters to trigger the
metric computation. For that I have added a compute route and removed
routes which were dedicated for different metrics. Instead I am now
passing the metric type via HTTP POST request.

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