[WIP] Add in-game level editor

[Alberth289346]

*Fixes #level-editor-is-missing

Attempts to make the level editor more reachable for our users by integrating it in he game.

• As the number of settings is large, I opted for constructing string names from the name of the setting in the level config file.
• pos_size.lua adds 2 classes for wrapping position x/y and size w/h as a single value.
• tree_access.lua can read/write nested tables using paths expressed in strings, _S works too.
• level_editor/data_storage.lua adds classes for data of the level editor:
  • LevelValue represents a value in a level config file with its data,
  • LevelValuesSection class represents an editable list of LevelValue.
  • LevelTableSection class does the same, except for a matrix of values.
  • LevelEditPage organizes one or more of the above sections into a "screen".
  • LevelTabPage manages all edit pages by being able to select "tab"s for the page to be shown.
• UILevelEditor the level editor main window class.

I am in the process of adding more table sections.

Stuff notably missing:

• No UI access to the level editor as a whole. While the main menu can open it, you cannot close it. You can also not load or save level data (There is code for collecting and updating LevelValues to/from a nested tree of tables, but that is never called currently. I am not sure where to add these.

Stuff notably ignored:

• There is ample room for improvements I am sure.

[Alberth289346]

Some notes about the current state.

• All 30 screens with data values editing have been added, and they all fit in the 640x480 screen assumption.
• You can open the level editor from the main menu.
• Screen selection also works.

Converting editor data back and forth to nested tables worked in a previous version, and should still work, as there are no changes done since in that area. Entry point for both is loadStoreCfg(table, direction).
I opted for using the original value names in the level configuration. They are slightly different from base_config.lua, since that tree has .Value added at some points, added by the current level config file loader.

Load and save from/to the file sytstem can easily be implemented with TreeAccess (also tested in a previous version). Currently "save" needs a template to decide where to save what information. The template can also contain the comments.

Missing:

• No UI for load/save, and for exiting the level editor yet.
• A save template level config if that is the decided direction.
• The windowing code doesn't honor invisibility correctly. It's possible to activate an invisible textbox for editing which is less than useful.

Other things:

• Someone should check that the English texts makes sense.

Future optional enhancements:

• In development, I wrote a Python script that takes a sequence of name1.name2.name.,nameX, = "some text" lines, and converts it to a nested table like in english.lua. That could be adopted if so desired.
• Organizing the settings into useful screens hasn't had much attention. Some values can likely be deleted (eg unused objects), or similar objects / topics can be moved closer to each other.
• Some details are silly to a user, eg left entrance and right entrance door as 2 separate objects. The editor should hide such details.
• "List-like" settings, like emergencies, win conditions, etc currently have a fixed number of entries (typically far smaller than is allowed). That should be extended to allow adding more entries to the list.
• Everything is a numeric value, while from a user point of view, a checkmark (for boolean values), a drop-down (for a limited number of allowed values), or a graph in time (for eg number of patients, emergencies, etc) would be much more readable.