Finished implementing "Delete Effect(s)" button

Added functionality to decrease each effect's remaining rounds at the
start of a new round. Added functionality to prompt user to remove any
effects that have reached 0 (this might be better if the user is
prompted at the start of each combatant's turn rather than dealing with
it all at once. Adjustments may be forgotten).

Thinking of adding "Batch Add" section to "Add ..." dialog. Basically
the user can choose to add a batch of identical combatants to the fight.
They provide a base name (e.g. Goblin) and the program will create
Goblin #1, Goblin #2, etc. The user also provides an expression for HP
(e.g. 1d8+1) which the program uses to generate individual HP. Will
require R&D into random number generation in C#.
Began implementing "Batch Add" functionality

Just need to write the code that verifies input upon clicking "OK" and
creates the combatants for the initiative list.