Two new [message] features

- ~LEFT() does the opposite of ~RIGHT(), but takes higher priority;
  use it to force an image to the left that's normally on the right
  (eg female silver mage)
- image=~RIGHT() means "use normal portrait, but on the right"

data/core/units/humans/Mage_Silver.cfg

@@ -161,7 +161,7 @@ Silver magi are often more physically adept than other magi, and their skills ar
         name= _ "female^Silver Mage"
         gender=female
         image="units/human-magi/silver-mage+female.png"
-        profile="portraits/humans/mage-silver+female.png"
+        profile="portraits/humans/mage-silver+female.png~LEFT()"
         die_sound={SOUND_LIST:HUMAN_FEMALE_DIE}
         {DEFENSE_ANIM "units/human-magi/silver-mage+female-defend.png" "units/human-magi/silver-mage+female.png" {SOUND_LIST:HUMAN_FEMALE_HIT} }
         [attack_anim]

data/lua/wml/message.lua

@@ -13,16 +13,36 @@ end
 
 local function get_image(cfg, speaker)
 	local image = cfg.image
+	local left_side = true
+	
+	if image == "~RIGHT()" then
+		image = nil
+		left_side = false
+	end
 
 	if speaker and (image == nil or image == "") then
 		image = speaker.portrait
 	end
 
-	if image == "none" or image == nil then
-		return ""
+	if image:find("~RIGHT%(%)") then
+		left_side = false
+		-- The percent signs escape the parentheses for a literal match
+		image = image:gsub("~RIGHT%(%)", "")
 	end
 
-	return image
+	if image:find("~LEFT%(%)") then
+		-- This currently overrides ~RIGHT()
+		-- Use if a portrait defaults to ~RIGHT(),
+		-- or in [unit_type] to force it to left.
+		left_side = true
+		image = image:gsub("~LEFT%(%)", "")
+	end
+
+	if image == "none" or image == nil then
+		return "", true
+	end
+
+	return image, left_side
 end
 
 local function get_caption(cfg, speaker)
@@ -53,17 +73,9 @@ local function get_speaker(cfg)
 end
 
 local function message_user_choice(cfg, speaker, options, text_input)
-	local image = get_image(cfg, speaker)
+	local image, left_side = get_image(cfg, speaker)
 	local caption = get_caption(cfg, speaker)
 
-	local left_side = true
-	-- If this doesn't work, might need tostring()
-	if image:find("~RIGHT()") then
-		left_side = false
-		-- The percent signs escape the parentheses for a literal match
-		image = image:gsub("~RIGHT%(%)", "")
-	end
-
 	local msg_cfg = {
 		left_side = left_side,
 		title = caption,