Lua settings improvements

[PilzAdam]

Changes:

• Key settings are added to minetest.conf.example
• Added missing key and noclip settings to `settingtypes.txt
• Expanded description on key settings
• Fixed parallax typos
• flags now fully supported with a list of possible values
• Added input validation for int, float and flags types (type safety and min / max checks)
• Restructured graphics section
• Additional settingtypes.txt files are passed from games and mods root folders; they are displayed in special categories.
• Added description for format of noise_params type

[kilbith]

@PilzAdam You've cancelled (at least) 9d21fa3 with 5675486.

[PilzAdam]

@kilbith Thanks for spotting that; I checked everything else now.

[PilzAdam]

Everything important is now done here, except the support for grouped noise param settings, but this is due to a missing Lua API functionality for grouped settings (or structs).

The only things missing from the list in #3266 are fancier input dialogs for certain types, but that's not so high priority.

I think this can be merged now.

[est31]

comman?

[PilzAdam]

Typo; will fix.

[est31]

Really great idea to scan for settingstypes.txt in the mods and game directories as well.

[est31]

For modders and game creators: should we add documentation for how to automatically generate minetest.conf.example for mods/games from settingstypes.txt?

[PilzAdam]

@est31 addressed all your remarks.

If we want to expose the generation of minetest.conf.example then it should be done with a command line option or an extra button in the GUI. Editing builtin/mainmenu/tab_settings.lua is not an option for end-users (on some distros they may not be able to edit this file, since it's installed in the system-wide part).

I would personally prefer a way to pass command-line options to the main menu (maybe with registering them first, so they can be printed in --help), but that may be too complicated for this use-case.

[rubenwardy]

"around"

[paramat]

New notes for map_generation_limit for settingtypes.txt and minetest.conf.example.
The unnecessary 'please note' line can be removed and the notes formatted as elsewhere in these files.

"Map generation is limited to this distance in nodes from (0, 0, 0),
along all axes in positive and negative directions.
Value is limited to 31000.
By default map generates in chunks of 80x80x80 nodes
that are offset by (-32, -32, -32) nodes from (0, 0, 0).
Only chunks within the map generation limit volume are generated."

[PilzAdam]

Thanks for all your suggestions on settingtypes.txt, but I'd like to first merge this PR, since it contains important functionality. Improving settingtypes.txt will probably take a long time and should be subject of future PRs.

[paramat]

Cool. For the moment don't worry too much about the setting of noise parameters, as this is advanced stuff that can always be done using minetest.conf.example.

[est31]

Don't edit that file anymore. If you want to change something in minetest.conf.example, edit settingstypes.txt instead, and @PilzAdam will generate minetest.conf.example with automated tools.