card_fields rewrite and magic-modules.mse-include (#21)

Overhauls the card_fields file to allow for template designers more freedom in manipulating data.

Adds magic-modules.mse-include, a large scale include file for building templates in a standardized way. Applying this to existing frames will be coming in future updates.

data/magic-modules.mse-include/rarities/choice_images

@@ -0,0 +1,39 @@
+choice images:
+	# Images based on the set symbol
+	basic land:
+		script:
+			if use_main_rarity() then mainframe_rarity("c")
+			else if alt_rarity() then alt_symbol()
+			else if styling.inverted_common_symbol or else set.inverted_common_symbol then symbol_variation(symbol: set.symbol, variation: "invertedcommon")
+			else symbol_variation(symbol: set.symbol, variation: "common")
+	common:
+		script:
+			if use_main_rarity() then mainframe_rarity("c")
+			else if alt_rarity() then alt_symbol()
+			else if styling.inverted_common_symbol or else set.inverted_common_symbol then symbol_variation(symbol: set.symbol, variation: "invertedcommon")
+			else symbol_variation(symbol: set.symbol, variation: "common")
+	uncommon:
+		script:
+			if use_main_rarity() then mainframe_rarity("u")
+			else if alt_rarity() then alt_symbol()
+			else symbol_variation(symbol: set.symbol, variation: "uncommon")
+	rare:
+		script:
+			if use_main_rarity() then mainframe_rarity("r")
+			else if alt_rarity() then alt_symbol()
+			else symbol_variation(symbol: set.symbol, variation: "rare")
+	mythic rare:
+		script:
+			if use_main_rarity() then mainframe_rarity("m")
+			else if alt_rarity() then alt_symbol()
+			else symbol_variation(symbol: set.symbol, variation: "mythic rare")
+	special:
+		script:
+			if use_main_rarity() then mainframe_rarity("s")
+			else if alt_rarity() then alt_symbol()
+			else symbol_variation(symbol: set.symbol, variation: "special")
+	masterpiece:
+		script:
+			if use_main_rarity() then mainframe_rarity("mp")
+			else symbol_variation(symbol: set.masterpiece_symbol, variation: "mythic rare")
+