-Changed the selection mode to extended selection on the lstCharacters tree-view. This will not affect anything else other than the "detailed info" rows. Every other change to a character's descriptions, motivations and such only affect the last selected one.
-Made a method to get all the IDs of the selected characters.
-Added a character-info dialog UI. Originally, adding information worked by adding a placeholder and then changing it. Users never want to just add a placeholder without initialising the values. And the bulk-adding only works this way.
