Refactor MenuPowers

This commit simplifies the how the data for MenuPowers is stored and
used. Base powers and upgrades are now link together, so handling
upgrades (and potential downgrades) is now much easier. Each cell, or
"group", contains its position data, a list of powers, and an index for
the currently enabled power.

Also added was a way to skip over invisible slots when using keyboard
navigation. Previously, these slots could be selected, but there would
be no indication as they weren't being rendered.

RELEASE_NOTES.txt

@@ -33,6 +33,7 @@ Engine fixes:
 * The user keybindings are now reset if the keybindings file is not forwards compatible. Anyone using remapped keys will need to set them again with this update.
 * Improved performance when dealing with campaign statuses.
 * Fix NPCs/enemies not begin affected by statuses set in on_load events until the player re-entered the map.
+* Various fixes to MenuPowers, including better handling of when powers no longer meet their requirements.
 * Lots of code cleanup.
 
 New translations:

src/EventManager.cpp

@@ -951,7 +951,7 @@ bool EventManager::executeEvent(Event &ev) {
  pc->stats.powers_list.push_back(pc_class->powers[j]);
  }
  }
- menu_powers->applyPowerUpgrades();
+ menu_powers->setUnlockedPowers();
 
  menu_act->clear();
  if (pc_class && !use_engine_defaults) {

src/MenuManager.cpp

@@ -115,7 +115,7 @@ MenuManager::MenuManager(StatBlock *_stats)
  mini = new MenuMiniMap();
  chr = new MenuCharacter(stats);
  inv = new MenuInventory(stats);
- pow = new MenuPowers(stats, act);
+ pow = new MenuPowers();
  questlog = new MenuLog();
  stash = new MenuStash(stats);
  book = new MenuBook();
@@ -1060,7 +1060,7 @@ void MenuManager::dragAndDropWithKeyboard() {
  // clear power dragging if power slot was pressed twice
  else if (slotClick == WidgetSlot::ACTIVATED) {
  if (drag_power > 0) {
- pow->upgradeByCell(slot_index);
+ pow->upgradeBySlotIndex(slot_index);
  }
  drag_src = DRAG_SRC_NONE;
  drag_power = 0;