Support for banned game entities in random map templates

The following entities can now be banned in a random map template
definition:
- Hero
- Artifact
- Spell
- Secondary skill

The ban follows the same rules as banning via the map settings in the
map editor.

It is also now possible to bypass dependencies and access identifiers
from mods that are not dependencies when defining:
- Banned entities in random map templates
- the chance of a hero class appearing in a tavern of a specific faction
- the chance of a spell appearing in a mage guild of a specific faction
- the chance of a hero class receiving a secondary skill

For this to work, the identifier must be specified in full, e.g.
`modName:objectName`. If the specified mod is not active, the game will
silently ignore this entry.

This behaviour is not affected by mod load order. It is possible to use
this format to access a mod that has not yet been loaded.

docs/modders/Entities_Format/Faction_Format.md

@@ -228,19 +228,26 @@ Each town requires a set of buildings (Around 30-45 buildings)
 
 	// Chance of specific hero class to appear in this town
 	// Mirrored version of field "tavern" from hero class format
+	/// Identifier without modID specifier MUST exist in base game or in one of dependencies
+	/// Identifier with explicit modID specifier will be silently skipped if corresponding mod is not loaded
 	"tavern" :
 	{
 		"knight" : 5,
-		"druid"  : 6
+		"druid"  : 6,
+		"modID:classFromMod" : 4
 	},
 
 	// Chance of specific spell to appear in mages guild of this town
 	// If spell is missing or set to 0 it will not appear unless set as "always present" in editor
 	// Spells from unavailable levels are not required to be in this list
+	/// Identifier without modID specifier MUST exist in base game or in one of dependencies
+	/// Identifier with explicit modID specifier will be silently skipped if corresponding mod is not loaded
+
 	"guildSpells" :
 	{
 		"magicArrow" : 30,
-		"bless"  : 10
+		"bless"  : 10,
+		"modID:spellFromMod" : 20
 	},
 
 	// Which tiers in this town have creature hordes. Set to -1 to disable horde(s)