Overhaul and improve force cages

- Add instant help message
- Prevent from ending town combat if one member is in a forcecage or if everyone's in a different forcecage (you can still end it if everyone's in the same cage)
- If entering town combat while caged, everyone remains in the cage
- Penalties to melee combat if the target or attacker is in a forcecage (higher penalties if the attacker is caged, unless they're using a pole weapon)
- Instead of placing a forcecage at every location where someone gains forcecage status, the game now syncs forcecages (placing them on locations where someone has forcecage status) at the end of the move.
- The Flash Step and Word of Recall spells and any specials that move the party also clear their forcecage status, so that a new forcecage won't appear on their new location. If they're moved into a forcecage, the syncing process will give them the status at the end of the move.
- Forcecage status now supported for the Occasional Status item ability
- Forcecages now eventually expire on their own even if you can't break out. Unoccupied ones also have a slight (0.1%) chance each turn to expire.
- Affect Status node now allows forcecage status. (It also works as documented, using Extra 1c rather than 2a as the status type.)
- Preset monsters placed in preset force cages gain the status at town initialization; it's a lot more than they'd gain through the syncing process, so unless they break free, it'll last a very long time.
- Monsters/PCs with spells (and PCs with Mage Lore) now have an increased chance of resisting entrapment in a forcecage
- If the full party is subject to a forcecage, the PC with the best chance of breaking free (assuming they don't resist) is chosen to determine whether they resist. Note that this may not be the PC with the best chance of resisting in the first place.
- Protection from Forcecage now implemented as an item ability
Other stuff (though related):
- Reset party's combat pos to the null location (-1,-1) after a cutscene ends; to not do so would mess up get_loc() calls

doc/editor/appendix/Specials.html

@@ -812,7 +812,11 @@ set Extra 1b to 0 if you want to help the party or 1 if you want to harm them.
 <dt>Extra 1a:</dt><dd>The amount to change. (Usually ranges is 0 ... 8; Martyr's Shield is
 0 ... 10, and paralysis is 0 ... 5000)</dd>
 <dt>Extra 1b:</dt><dd>If 0, helps. Otherwise, harms.</dd>
-<dt>Extra 1c:</dt><dd>Which status effect. Press the Choose button to select one.</dd></dd>
+<dt>Extra 1c:</dt><dd>Which status effect. Press the Choose button to select one.</dd>
+<dt>Note:</dt><dd>If you affect their forcecage status, a forcecage barrier will
+automatically be placed on the space. However, if you reduce their forcecage status to 0,
+it won't work because being in a forcecage barrier will reset their status. To free them
+from a forcecage, you should instead use Place Fields with the "Cleanse" type.</dd></dd>
 
 <dt>Type 88: Affect Traits</dt><dd>Adds or removes a special trait. If the target is a
 monster, this has no effect.
@@ -1776,7 +1780,12 @@ or sfx (16 - sm blood, 17 - med blood, 18 - lg blood, 19 - sm slime, 20 - lg sli
 21 - ash, 22 - bones, 23 - stones) to place, or one of the special values (32 - cleanse,
 33 - smash fragile walls like Move Mountains).</dd>
 <dt>Note:</dt><dd>Fields are never placed on spaces that contain walls, or other
-impenetrable terrain.</dd></dd>
+impenetrable terrain.</dd>
+<dt>Note:</dt><dd>Though you can place a forcecage around a creature using this, if you
+know which creature you want it's better to use Affect Status which allows you to control
+how long the forcecage will last (unless they manage to break it). If you want to free
+them from a forcecage, on the other hand, use this node with the special value 32
+("Cleanse").</dd></dd>
 
 <dt>Type 211: Set Explored</dt><dd>This node alters your map, marking spaces as having
 been explored or not.