Widget positions and a few other options (e.g. date formats) can be
specified in dfhack-config/dwarfmonitor.json on a per-instance basis.
Related changes:
* Fixed an issue loading JSON files from Lua
* JSON files in dfhack-config (only dwarfmonitor.json currently) are
no longer copied into the DF directory when building DFHack. This
keeps developers' personal settings intact, but will require
copying over changes made to DFHack's copies manually.
* Fixed incorrect config path in dwarfmonitor help