New features for players:
* Loading for multiplayer. Any save could be used for multiplayer.
* Restart for multiplayer. All clients will restart together.
* Loading from single save.
* Hotseat mixed with network game. Multiple players per client.
* Now connection to server could be cancelled.
* Return to menu on disconnections instead of crashes.
* Restoring of last selected map, save or campaign on next run.
TLDR on important changes in engine code:
* UI: work with server separated from UI
* UI: all explitic blitting replaced with IntObject's
* UI: all new code use smart pointers instead of DISPOSE
* Gameplay always start through lobby controlled by server.
* Threads receiving netpacks now shared for lobby and gameplay.
* Campaigns: heroes for crossover now serialized as JsonNode.
* Universities, Scholars and Witch Huts may offer new skills
* Moved encode/decodeSkill to CSkillHandler
* Refactored CSkill interface and CSkill::LevelInfo image storage
* Legacy game constants renamed to ORIGINAL_XXX_QUANTITY
Addresses several related problems:
* Propagation / unpropagation of duplicate bonuses is inconsistent, causing bugs
* Duplicate bonuses never stack, which is not always intended behaviour (e.g. multiple copies of resource generating artifacts)
* Different bonuses always stack, which is not always intended behaviour (e.g. Angel + Archangel morale bonuses)
This is addressed as follows:
* Duplicate bonuses are never eliminated during propagation/inheritance.
* Unpropagation eliminates only a single copy of duplicated bonus
* Bonus receives a new field stacking that determines stacking behaviour:
* * empty string = no stacking with duplicates (default)
* * "ALWAYS" = stacks with duplicates & everything else
* * some other value = no stacking with bonuses with same stacking value
Also Morale/Luck window now hides non-stacking bonuses.
* changed Bonus::additionalInfo to integer vector
* fixed deserialization for old savegames
* removed newline from JsonNode::toJson()
* updated bonus schema; SPELL_AFTER_ATTACK and SPELL_BEFORE_ATTACK use new addInfo format
* removed unnecessary init in Bonus constructor
