Implement level-up screens

[modawan]

There is some support already (attributes, skills), but feats selection screen is not implemented, so the process cannot be completed.
This blocks progress on Endar Spire, because the door from the bridge requires the player to be level 2.

Workaround: change GetHitDice to always return 2.

diff --git a/src/libs/game/script/routine/impl/main.cpp b/src/libs/game/script/routine/impl/main.cpp
index db07a116..13d95a17 100644
--- a/src/libs/game/script/routine/impl/main.cpp
+++ b/src/libs/game/script/routine/impl/main.cpp
@@ -1440,7 +1440,7 @@ static Variable GetHitDice(const std::vector<Variable> &args, const RoutineConte
     auto creature = checkCreature(oCreature);
 
     // Execute
-    return Variable::ofInt(creature->attributes().getAggregateLevel());
+    return Variable::ofInt(2);
 }
 
 static Variable GetTag(const std::vector<Variable> &args, const RoutineContext &ctx) {

[modawan]

With #67 level up process can be completed, but Feats and Force Powers pages are still missing.