🔧 Settings file

As of 58d3b464, app parameters (needed by files like src/init.js or src/router.js) are hard-coded.
For example, databases are listed as a parameter of the Loader construction.

All relevant settings (begginning with the list of databases cited above) should come from a settings file, for example a settings.json or something like that.

I'm not sure yet where this file should be committed. /public would be the obvious choice, or maybe /resources.
However, as one of the usecases of Hecate is to be forked and modified by non-developpers, having such a file directly at the root of the repository has advantages. On the other hands, maybe just one file won't be enough, as in the end we might need multiple ones (one for the instance configuration, a second for each databases specific behaviour, one for styles, ...).