improve(API): prevent API requests when not authenticated
improve(auth): avoid using authentication.changed

This prevents some unexpected behaviors.
improve(directives): isolate scopes of tasks list and task details
fix(task form): prevent task without form to be flagged as invalid
fix(tasks): reload tasks when a filter is changed
improve(misc): unregister event listeners when scopes are destroyed

Related to: CAM-2783
feat(filter): display the amount of tasks for a filter

Related to: CAM-2755
style(task): format code and remove some commented chunks
refactor(diagram): uncomment the diagram tab

refactor(diagram): update the bpmn-js bower package
fix(diagram): correct highlighted diagram element style
fix(diagram): bind Snap.svg to the window object before loading bpmn-js

Related to: CAM-2652
fix(filter): correct the filter creation authorization check
fix(filter): validate the general information

Related to: CAM-2807
Merge branch 'master' of github.com:camunda/camunda-tasklist