Provide integration with a Kimai instance

[lenucksi]

Motivation

This app looks nice, however if one ends up having to track time with multiple devices, it's nice to have it stored in a central location. Also this allows for easier reporting.

Proposal

There is a web application called Kimai (https://github.com/kimai/kimai) for which there a number of clients, which is actively developed and whose functionality is acceptably good. Also they provide a sort of API on a JSON basis. It would be lovely if ATimeTracker could sync its entry with this web application.