Issue #12 & #14

Implementation of issue #12 and #14 (Edit and create a new activity)
The UI is pretty basic and surely need improvements, but the controller code and structure is in place.

(Live demo) [https://gdetracking.gweb.io/hist/mauro/Issue-12_14/]

P.S. Pull request can't be automerged merging manually after some checking but other pairs of eyes :)