Introduce generalised live loading of widgets for dashboard

We can use django-live-templates for that.

To do:

• Find out how apps can provide widgets
• Find out how users can add/remove/order widgets
• Test and maybe use django-live-templates to build the template

@ZugBahnHof Maybe we should do a one-on-one video chat on this to plan it.

changed milestone to %2.0a2

added part::backend part::frontend workflow::discussing labels

mentioned in issue #134 (closed)

marked the checklist item Find out how apps can provide widgets as completed

mentioned in commit fb3561d3

mentioned in commit 3f4712db

mentioned in commit 1532c964

mentioned in commit b1401f76

mentioned in commit 7d553ae3

added workflow::confirmed label and removed 1 deleted label

added part::backend part::frontend labels

Closed as sub-tasks are tracked in separate issues now.

closed