minor fix for TrueSkillLimit plugin

(skill changes weren't taken into account dynamically)
Use _DEFAULT_ syntax for TrueSkillLimit conf file
new plugin customization callback setMapStartBoxes

getDefaultModOptions.pl: 0.4d
  . fix setting ranges and negative values handling

spads.pl: 0.11.19
  . new plugin customization callback "setMapStartBoxes"
  . fix setting ranges and negative values handling
  . print message in battle and game when a plugin setting is changed

SpadsPluginApi.pm: 0.11
  . new plugin customization callback "setMapStartBoxes"