Support (some) json file formats

[Kittyfisto]

As part of the proof of concept of the tabular log file viewer, Tailviewer should start supporting one or the other json log file format (TODO: Research how many there are and pick the most popular ones if there's multiple).

Opening such a log file should display one column per property and create the columns on-demand, if possible, based on the contents of the particular log file.

TODO: Add more requirements.