Script API: expand methods for displaying list of files and saves

[ivan-mogilko]

Fix #816

This PR is a collection of additions, with the primary purpose to customize a list of saves that player may have in game, and remove existing historical limitation of 50 saves in list. It backports "range of slots" support in FilleSaveGameList (#2293) to 3.6.2, adds ability to retrieve file write times, and sort files in different order when using ListBox.FillDirList. The latter may be useful (besides other things) when making custom save lists.

Full list of additions.

1. Backport of AGS 4: Script API: in FillSaveGameList() accept a range of slots #2293:

• FillSaveGameList, RestoreGameDialog and SaveGameDialog support range of slots to display (1 - 50 by default, or in backwards mode)
• Save slots no longer rearranged when calling DeleteSaveSlot (except when in backwards mode).
• Added MoveSaveSlot() in case user wants to replicate this behavior (or for other uses).

2. Added a config option "max_save" in "[override]" group that lets to manually set topmost save slot for standard save/restore dialogs. This is for MAXSAVEGAMES 50 #816, and primarily purposed for playing old games.
3. New functions for getting file time:

• static DateTime* File.GetFileTime(name)
• static DateTime* Game.GetSaveSlotTime(saveSlot) - to accompany Game.GetSaveSlotDescription().

4. ListBox.FillDirList() now supports sorting style and direction.

enum FileSortStyle
{
  eFileSort_None = 0,
  eFileSort_Name = 1,
  eFileSort_Time = 2
};

enum SortDirection
{
  eSortNoDirection = 0,
  eSortAscending   = 1,
  eSortDescending  = 2
};

void ListBox.FillDirList(const string fileMask,
                      FileSortStyle fileSortStyle = eFileSort_Name,
                      SortDirection sortDirection = eSortAscending);

[ivan-mogilko]

Added a config option "max_save" in "[override]" group that lets to manually set topmost save slot for standard save/restore dialogs. This is for #816, and primarily purposed for playing old games.
It affects standard save/restore dialogs filled with list of saves. It won't (and technically cannot) affect any custom made save system.